Combining two expressions (Expression<Func>)

205

I have two expressions of type Expression<Func<T, bool>> and I want to take to OR, AND or NOT of these and get a new expression of the same type

Expression<Func<T, bool>> expr1;

Expression<Func<T, bool>> expr2;



...



//how to do this (the code below will obviously not work)

Expression<Func<T, bool>> andExpression = expr AND expr2

edited Jun 27 '09 at 1:04

andy

4,2341160108

asked Jan 19 '09 at 11:29

BjartN

2,07042030

7

Very useful post I got from Google: LINQ to Entities: Combining Predicates
– Thomas C. G. de Vilhena
Jan 1 '14 at 18:23

add a comment |

205

I have two expressions of type Expression<Func<T, bool>> and I want to take to OR, AND or NOT of these and get a new expression of the same type

Expression<Func<T, bool>> expr1;

Expression<Func<T, bool>> expr2;



...



//how to do this (the code below will obviously not work)

Expression<Func<T, bool>> andExpression = expr AND expr2

edited Jun 27 '09 at 1:04

andy

4,2341160108

asked Jan 19 '09 at 11:29

BjartN

2,07042030

7

Very useful post I got from Google: LINQ to Entities: Combining Predicates
– Thomas C. G. de Vilhena
Jan 1 '14 at 18:23

add a comment |

205

I have two expressions of type Expression<Func<T, bool>> and I want to take to OR, AND or NOT of these and get a new expression of the same type

Expression<Func<T, bool>> expr1;

Expression<Func<T, bool>> expr2;



...



//how to do this (the code below will obviously not work)

Expression<Func<T, bool>> andExpression = expr AND expr2

edited Jun 27 '09 at 1:04

andy

4,2341160108

asked Jan 19 '09 at 11:29

BjartN

2,07042030

I have two expressions of type Expression<Func<T, bool>> and I want to take to OR, AND or NOT of these and get a new expression of the same type

Expression<Func<T, bool>> expr1;

Expression<Func<T, bool>> expr2;



...



//how to do this (the code below will obviously not work)

Expression<Func<T, bool>> andExpression = expr AND expr2

c# linq lambda expression

edited Jun 27 '09 at 1:04

andy

4,2341160108

asked Jan 19 '09 at 11:29

BjartN

2,07042030

edited Jun 27 '09 at 1:04

andy

4,2341160108

asked Jan 19 '09 at 11:29

BjartN

2,07042030

edited Jun 27 '09 at 1:04

andy

4,2341160108

edited Jun 27 '09 at 1:04

andy

4,2341160108

edited Jun 27 '09 at 1:04

andy

4,2341160108

asked Jan 19 '09 at 11:29

BjartN

2,07042030

asked Jan 19 '09 at 11:29

BjartN

2,07042030

asked Jan 19 '09 at 11:29

BjartN

2,07042030

7

Very useful post I got from Google: LINQ to Entities: Combining Predicates
– Thomas C. G. de Vilhena
Jan 1 '14 at 18:23

add a comment |

7

Very useful post I got from Google: LINQ to Entities: Combining Predicates
– Thomas C. G. de Vilhena
Jan 1 '14 at 18:23

Very useful post I got from Google: LINQ to Entities: Combining Predicates
– Thomas C. G. de Vilhena
Jan 1 '14 at 18:23

add a comment |

7 Answers
7

active

oldest

votes

259

Well, you can use Expression.AndAlso / OrElse etc to combine logical expressions, but the problem is the parameters; are you working with the same ParameterExpression in expr1 and expr2? If so, it is easier:

var body = Expression.AndAlso(expr1.Body, expr2.Body);

var lambda = Expression.Lambda<Func<T,bool>>(body, expr1.Parameters[0]);

This also works well to negate a single operation:

static Expression<Func<T, bool>> Not<T>(

    this Expression<Func<T, bool>> expr)

{

    return Expression.Lambda<Func<T, bool>>(

        Expression.Not(expr.Body), expr.Parameters[0]);

}

Otherwise, depending on the LINQ provider, you might be able to combine them with Invoke:

// OrElse is very similar...

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> left,

    Expression<Func<T, bool>> right)

{

    var param = Expression.Parameter(typeof(T), "x");

    var body = Expression.AndAlso(

            Expression.Invoke(left, param),

            Expression.Invoke(right, param)

        );

    var lambda = Expression.Lambda<Func<T, bool>>(body, param);

    return lambda;

}

Somewhere, I have got some code that re-writes an expression-tree replacing nodes to remove the need for Invoke, but it is quite lengthy (and I can't remember where I left it...)

Generalized version that picks the simplest route:

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> expr1,

    Expression<Func<T, bool>> expr2)

{

    // need to detect whether they use the same

    // parameter instance; if not, they need fixing

    ParameterExpression param = expr1.Parameters[0];

    if (ReferenceEquals(param, expr2.Parameters[0]))

    {

        // simple version

        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(expr1.Body, expr2.Body), param);

    }

    // otherwise, keep expr1 "as is" and invoke expr2

    return Expression.Lambda<Func<T, bool>>(

        Expression.AndAlso(

            expr1.Body,

            Expression.Invoke(expr2, param)), param);

}

Starting from .net 4.0. There is the ExpressionVistor class which allows you to build expressions that are EF safe.

    public static Expression<Func<T, bool>> AndAlso<T>(

        this Expression<Func<T, bool>> expr1,

        Expression<Func<T, bool>> expr2)

    {

        var parameter = Expression.Parameter(typeof (T));



        var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);

        var left = leftVisitor.Visit(expr1.Body);



        var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);

        var right = rightVisitor.Visit(expr2.Body);



        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(left, right), parameter);

    }







    private class ReplaceExpressionVisitor

        : ExpressionVisitor

    {

        private readonly Expression _oldValue;

        private readonly Expression _newValue;



        public ReplaceExpressionVisitor(Expression oldValue, Expression newValue)

        {

            _oldValue = oldValue;

            _newValue = newValue;

        }



        public override Expression Visit(Expression node)

        {

            if (node == _oldValue)

                return _newValue;

            return base.Visit(node);

        }

    }

edited Feb 27 '15 at 10:55

user3934443

answered Jan 19 '09 at 11:32

Marc Gravell♦

777k19221262539

Hey Marc, I tried out your first suggestion, in the your first code block above, but when I pass in the "lambda" expression<func<T,bool>> result in a Where method, I get an error saying the parameter is out of scope? any idea? cheers
– andy
Jun 27 '09 at 5:52

1

+1 the generalized version works like a charm, I used And instead of andalso, I thought linq to sql doesn't support andalso?
– Maslow
Sep 4 '09 at 13:57

2

@Maslow - here's a rewriter that can inline the trees to save Invoke: stackoverflow.com/questions/1717444/…
– Marc Gravell♦
Mar 19 '11 at 21:12

1

@Aron now look at the date: the .NET framework visitor (ExpressionVisitor) did not exist back then; I have a related example on stackoverflow from a similar date where it implements the visitor manually: it is a lot of code.
– Marc Gravell♦
Aug 13 '14 at 7:09

1

@MarkGravell, I'm using your first solution to combine my expressions, and everything is working fine even in entityframework, So what would the benefits of using the last solution be?
– johnny 5
Aug 3 '17 at 0:08

|
show 16 more comments

You can use Expression.AndAlso / OrElse to combine logical expressions, but you have to make sure the ParameterExpressions are the same.

I was having trouble with EF and the PredicateBuilder so I made my own without resorting to Invoke, that I could use like this:

var filterC = filterA.And(filterb);

Source code for my PredicateBuilder:

public static class PredicateBuilder {



    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.AndAlso(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }



    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.OrElse(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }   

}

And the utility class to substitute the parameters in a lambda:

internal class SubstExpressionVisitor : System.Linq.Expressions.ExpressionVisitor {

        public Dictionary<Expression, Expression> subst = new Dictionary<Expression, Expression>();



        protected override Expression VisitParameter(ParameterExpression node) {

            Expression newValue;

            if (subst.TryGetValue(node, out newValue)) {

                return newValue;

            }

            return node;

        }

    }

answered Sep 19 '12 at 14:53

Adam Tegen

13.8k30109145

This solution was the only one that allowed me to have x => x.Property == Value combined with arg => arg.Property2 == Value. Major props, a little terse and confusing but it works so I'm not going to complain. Kudos Adam :-)
– VulgarBinary
Dec 12 '12 at 20:38

Thanks. I've found the code useful in a lot of places.
– Adam Tegen
Dec 13 '12 at 19:10

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:26

Adam, this solved a very annoying problem I was having using the SharePoint Client Object model's Linq provider - thanks for posting it.
– Christopher McAtackney
Jul 9 '14 at 14:30

This worked for me! I had searched for a variety of solutions as well as predicate builder and nothing worked until this. Thank you!
– tokyo0709
Aug 1 '16 at 20:10

|
show 1 more comment

Joe Albahari (Author of C# 3.0 in a Nutshell and LINQPad) wrote a utility called PredicateBuilder which can be used to AND and OR functions together.

http://www.albahari.com/nutshell/predicatebuilder.aspx

While it works on functions it is open source so you can check it out and see how it works.

answered Jan 19 '09 at 22:52

Cameron MacFarland

52.2k1892120

1

The best solution!! The choosen answer is not as clear as the PredicatedBuilder solution. +1 for that!
– Eduardo Xavier
Oct 17 '11 at 16:51

@Eduardo: I disagree. PredicateBuilder's code is largely identical to the chosen answer, but the chosen answer provides explanation/code directly instead of via link.
– Brian
Mar 30 '12 at 15:37

4

PredicateBuilder DOES NOT WORK IN EF!!!!!!!!!!!!!!! It evaluates the query from the server then applies the desired predicate in memory instead of passing the predicate to SQL to restrict the result set. This is why PredicateBuilder is not desirable for this use case! BUYER BEWARE
– VulgarBinary
Dec 12 '12 at 20:40

@VulgarBinary Perhaps you could spend some time figuring out why it doesn't work in EF5 instead of waiting for the answer to be spoon-fed to you.
– Cameron MacFarland
Dec 13 '12 at 0:39

1

@CameronMacFarland I had already written a new PredicateBuilder myself that works and optimizes the expression trees. This snippet gave me the last piece I needed which was the visitor component. I was hardly waiting for anything to be spoon fed, if you seriously want your points back that badly edit your response and I'll take back the -1. However, when someone is looking to do something with Expression<Func<T,bool>> it generally means they want to use EF. Otherwise they would just have used Func<T,bool>
– VulgarBinary
Dec 13 '12 at 1:01

|
show 3 more comments

If you provider does not support Invoke and you need to combine two expression, you can use an ExpressionVisitor to replace the parameter in the second expression by the parameter in the first expression.

class ParameterUpdateVisitor : ExpressionVisitor

{

    private ParameterExpression _oldParameter;

    private ParameterExpression _newParameter;



    public ParameterUpdateVisitor(ParameterExpression oldParameter, ParameterExpression newParameter)

    {

        _oldParameter = oldParameter;

        _newParameter = newParameter;

    }



    protected override Expression VisitParameter(ParameterExpression node)

    {

        if (object.ReferenceEquals(node, _oldParameter))

            return _newParameter;



        return base.VisitParameter(node);

    }

}



static Expression<Func<T, bool>> UpdateParameter<T>(

    Expression<Func<T, bool>> expr,

    ParameterExpression newParameter)

{

    var visitor = new ParameterUpdateVisitor(expr.Parameters[0], newParameter);

    var body = visitor.Visit(expr.Body);



    return Expression.Lambda<Func<T, bool>>(body, newParameter);

}



[TestMethod]

public void ExpressionText()

{

    string text = "test";



    Expression<Func<Coco, bool>> expr1 = p => p.Item1.Contains(text);

    Expression<Func<Coco, bool>> expr2 = q => q.Item2.Contains(text);

    Expression<Func<Coco, bool>> expr3 = UpdateParameter(expr2, expr1.Parameters[0]);



    var expr4 = Expression.Lambda<Func<Recording, bool>>(

        Expression.OrElse(expr1.Body, expr3.Body), expr1.Parameters[0]);



    var func = expr4.Compile();



    Assert.IsTrue(func(new Coco { Item1 = "caca", Item2 = "test pipi" }));

}

edited Dec 13 '12 at 15:18

answered Dec 15 '11 at 15:36

Francis

2,7371243

1

This solved my particular problem where the other solution resulted in the same exception. Thanks.
– Shaun Wilson
Mar 7 '13 at 23:49

1

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:25

add a comment |

I suggest one more improvement to PredicateBuilder and ExpressionVisitor solutions. I called it UnifyParametersByName and you can find it in MIT library of mine: LinqExprHelper. It allows for combining arbitary lambda expressions. Usually the questions are asked about predicate expression, but this idea extends to projection expressions as well.

The following code employs a method ExprAdres which creates a complicated parametrized expression, using inline lambda. This complicated expression is coded only once, and then reused, thanks to the LinqExprHelper mini-library.

public IQueryable<UbezpExt> UbezpFull

{

    get

    {

        System.Linq.Expressions.Expression<

            Func<UBEZPIECZONY, UBEZP_ADRES, UBEZP_ADRES, UbezpExt>> expr =

            (u, parAdrM, parAdrZ) => new UbezpExt

            {

                Ub = u,

                AdrM = parAdrM,

                AdrZ = parAdrZ,

            };



        // From here an expression builder ExprAdres is called.

        var expr2 = expr

            .ReplacePar("parAdrM", ExprAdres("M").Body)

            .ReplacePar("parAdrZ", ExprAdres("Z").Body);

        return UBEZPIECZONY.Select((Expression<Func<UBEZPIECZONY, UbezpExt>>)expr2);

    }

}

And this is the subexpression building code:

public static Expression<Func<UBEZPIECZONY, UBEZP_ADRES>> ExprAdres(string sTyp)

{

    return u => u.UBEZP_ADRES.Where(a => a.TYP_ADRESU == sTyp)

        .OrderByDescending(a => a.DATAOD).FirstOrDefault();

}

What I tried to achieve was to perform parametrized queries without need to copy-paste and with ability to use inline lambdas, which are so pretty. Without all these helper-expression stuff, I would be forced to create whole query in one go.

answered Oct 16 '16 at 20:46

Jarekczek

5,01913050

add a comment |

I needed to achieve the same results, but using something more generic (as the type was not known). Thanks to marc's answer I finally figured out what I was trying to achieve:

    public static LambdaExpression CombineOr(Type sourceType, LambdaExpression exp, LambdaExpression newExp) 

    {

        var parameter = Expression.Parameter(sourceType);



        var leftVisitor = new ReplaceExpressionVisitor(exp.Parameters[0], parameter);

        var left = leftVisitor.Visit(exp.Body);



        var rightVisitor = new ReplaceExpressionVisitor(newExp.Parameters[0], parameter);

        var right = rightVisitor.Visit(newExp.Body);



        var delegateType = typeof(Func<,>).MakeGenericType(sourceType, typeof(bool));

        return Expression.Lambda(delegateType, Expression.Or(left, right), parameter);

    }

answered Jun 1 '17 at 12:48

VorTechS

171210

add a comment |

-7

I think this works fine, isn't it ?

Func<T, bool> expr1 = (x => x.Att1 == "a");

Func<T, bool> expr2 = (x => x.Att2 == "b");

Func<T, bool> expr1ANDexpr2 = (x => expr1(x) && expr2(x));

Func<T, bool> expr1ORexpr2 = (x => expr1(x) || expr2(x));

Func<T, bool> NOTexpr1 = (x => !expr1(x));

answered Nov 13 '15 at 15:11

Céline

1

this cannot be used in Linq to SQL for instance
– Romain Vergnory
May 12 '16 at 9:47

add a comment |

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7 Answers
7

active

oldest

votes

7 Answers
7

active

oldest

votes

259

var body = Expression.AndAlso(expr1.Body, expr2.Body);

var lambda = Expression.Lambda<Func<T,bool>>(body, expr1.Parameters[0]);

This also works well to negate a single operation:

static Expression<Func<T, bool>> Not<T>(

    this Expression<Func<T, bool>> expr)

{

    return Expression.Lambda<Func<T, bool>>(

        Expression.Not(expr.Body), expr.Parameters[0]);

}

Otherwise, depending on the LINQ provider, you might be able to combine them with Invoke:

// OrElse is very similar...

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> left,

    Expression<Func<T, bool>> right)

{

    var param = Expression.Parameter(typeof(T), "x");

    var body = Expression.AndAlso(

            Expression.Invoke(left, param),

            Expression.Invoke(right, param)

        );

    var lambda = Expression.Lambda<Func<T, bool>>(body, param);

    return lambda;

}

Somewhere, I have got some code that re-writes an expression-tree replacing nodes to remove the need for Invoke, but it is quite lengthy (and I can't remember where I left it...)

Generalized version that picks the simplest route:

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> expr1,

    Expression<Func<T, bool>> expr2)

{

    // need to detect whether they use the same

    // parameter instance; if not, they need fixing

    ParameterExpression param = expr1.Parameters[0];

    if (ReferenceEquals(param, expr2.Parameters[0]))

    {

        // simple version

        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(expr1.Body, expr2.Body), param);

    }

    // otherwise, keep expr1 "as is" and invoke expr2

    return Expression.Lambda<Func<T, bool>>(

        Expression.AndAlso(

            expr1.Body,

            Expression.Invoke(expr2, param)), param);

}

Starting from .net 4.0. There is the ExpressionVistor class which allows you to build expressions that are EF safe.

    public static Expression<Func<T, bool>> AndAlso<T>(

        this Expression<Func<T, bool>> expr1,

        Expression<Func<T, bool>> expr2)

    {

        var parameter = Expression.Parameter(typeof (T));



        var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);

        var left = leftVisitor.Visit(expr1.Body);



        var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);

        var right = rightVisitor.Visit(expr2.Body);



        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(left, right), parameter);

    }







    private class ReplaceExpressionVisitor

        : ExpressionVisitor

    {

        private readonly Expression _oldValue;

        private readonly Expression _newValue;



        public ReplaceExpressionVisitor(Expression oldValue, Expression newValue)

        {

            _oldValue = oldValue;

            _newValue = newValue;

        }



        public override Expression Visit(Expression node)

        {

            if (node == _oldValue)

                return _newValue;

            return base.Visit(node);

        }

    }

edited Feb 27 '15 at 10:55

user3934443

answered Jan 19 '09 at 11:32

Marc Gravell♦

777k19221262539

Hey Marc, I tried out your first suggestion, in the your first code block above, but when I pass in the "lambda" expression<func<T,bool>> result in a Where method, I get an error saying the parameter is out of scope? any idea? cheers
– andy
Jun 27 '09 at 5:52

1

+1 the generalized version works like a charm, I used And instead of andalso, I thought linq to sql doesn't support andalso?
– Maslow
Sep 4 '09 at 13:57

2

@Maslow - here's a rewriter that can inline the trees to save Invoke: stackoverflow.com/questions/1717444/…
– Marc Gravell♦
Mar 19 '11 at 21:12

1

@Aron now look at the date: the .NET framework visitor (ExpressionVisitor) did not exist back then; I have a related example on stackoverflow from a similar date where it implements the visitor manually: it is a lot of code.
– Marc Gravell♦
Aug 13 '14 at 7:09

1

@MarkGravell, I'm using your first solution to combine my expressions, and everything is working fine even in entityframework, So what would the benefits of using the last solution be?
– johnny 5
Aug 3 '17 at 0:08

|
show 16 more comments

259

var body = Expression.AndAlso(expr1.Body, expr2.Body);

var lambda = Expression.Lambda<Func<T,bool>>(body, expr1.Parameters[0]);

This also works well to negate a single operation:

static Expression<Func<T, bool>> Not<T>(

    this Expression<Func<T, bool>> expr)

{

    return Expression.Lambda<Func<T, bool>>(

        Expression.Not(expr.Body), expr.Parameters[0]);

}

Otherwise, depending on the LINQ provider, you might be able to combine them with Invoke:

// OrElse is very similar...

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> left,

    Expression<Func<T, bool>> right)

{

    var param = Expression.Parameter(typeof(T), "x");

    var body = Expression.AndAlso(

            Expression.Invoke(left, param),

            Expression.Invoke(right, param)

        );

    var lambda = Expression.Lambda<Func<T, bool>>(body, param);

    return lambda;

}

Somewhere, I have got some code that re-writes an expression-tree replacing nodes to remove the need for Invoke, but it is quite lengthy (and I can't remember where I left it...)

Generalized version that picks the simplest route:

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> expr1,

    Expression<Func<T, bool>> expr2)

{

    // need to detect whether they use the same

    // parameter instance; if not, they need fixing

    ParameterExpression param = expr1.Parameters[0];

    if (ReferenceEquals(param, expr2.Parameters[0]))

    {

        // simple version

        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(expr1.Body, expr2.Body), param);

    }

    // otherwise, keep expr1 "as is" and invoke expr2

    return Expression.Lambda<Func<T, bool>>(

        Expression.AndAlso(

            expr1.Body,

            Expression.Invoke(expr2, param)), param);

}

Starting from .net 4.0. There is the ExpressionVistor class which allows you to build expressions that are EF safe.

    public static Expression<Func<T, bool>> AndAlso<T>(

        this Expression<Func<T, bool>> expr1,

        Expression<Func<T, bool>> expr2)

    {

        var parameter = Expression.Parameter(typeof (T));



        var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);

        var left = leftVisitor.Visit(expr1.Body);



        var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);

        var right = rightVisitor.Visit(expr2.Body);



        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(left, right), parameter);

    }







    private class ReplaceExpressionVisitor

        : ExpressionVisitor

    {

        private readonly Expression _oldValue;

        private readonly Expression _newValue;



        public ReplaceExpressionVisitor(Expression oldValue, Expression newValue)

        {

            _oldValue = oldValue;

            _newValue = newValue;

        }



        public override Expression Visit(Expression node)

        {

            if (node == _oldValue)

                return _newValue;

            return base.Visit(node);

        }

    }

edited Feb 27 '15 at 10:55

user3934443

answered Jan 19 '09 at 11:32

Marc Gravell♦

777k19221262539

Hey Marc, I tried out your first suggestion, in the your first code block above, but when I pass in the "lambda" expression<func<T,bool>> result in a Where method, I get an error saying the parameter is out of scope? any idea? cheers
– andy
Jun 27 '09 at 5:52

1

+1 the generalized version works like a charm, I used And instead of andalso, I thought linq to sql doesn't support andalso?
– Maslow
Sep 4 '09 at 13:57

2

@Maslow - here's a rewriter that can inline the trees to save Invoke: stackoverflow.com/questions/1717444/…
– Marc Gravell♦
Mar 19 '11 at 21:12

1

@Aron now look at the date: the .NET framework visitor (ExpressionVisitor) did not exist back then; I have a related example on stackoverflow from a similar date where it implements the visitor manually: it is a lot of code.
– Marc Gravell♦
Aug 13 '14 at 7:09

1

@MarkGravell, I'm using your first solution to combine my expressions, and everything is working fine even in entityframework, So what would the benefits of using the last solution be?
– johnny 5
Aug 3 '17 at 0:08

|
show 16 more comments

259

var body = Expression.AndAlso(expr1.Body, expr2.Body);

var lambda = Expression.Lambda<Func<T,bool>>(body, expr1.Parameters[0]);

This also works well to negate a single operation:

static Expression<Func<T, bool>> Not<T>(

    this Expression<Func<T, bool>> expr)

{

    return Expression.Lambda<Func<T, bool>>(

        Expression.Not(expr.Body), expr.Parameters[0]);

}

Otherwise, depending on the LINQ provider, you might be able to combine them with Invoke:

// OrElse is very similar...

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> left,

    Expression<Func<T, bool>> right)

{

    var param = Expression.Parameter(typeof(T), "x");

    var body = Expression.AndAlso(

            Expression.Invoke(left, param),

            Expression.Invoke(right, param)

        );

    var lambda = Expression.Lambda<Func<T, bool>>(body, param);

    return lambda;

}

Somewhere, I have got some code that re-writes an expression-tree replacing nodes to remove the need for Invoke, but it is quite lengthy (and I can't remember where I left it...)

Generalized version that picks the simplest route:

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> expr1,

    Expression<Func<T, bool>> expr2)

{

    // need to detect whether they use the same

    // parameter instance; if not, they need fixing

    ParameterExpression param = expr1.Parameters[0];

    if (ReferenceEquals(param, expr2.Parameters[0]))

    {

        // simple version

        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(expr1.Body, expr2.Body), param);

    }

    // otherwise, keep expr1 "as is" and invoke expr2

    return Expression.Lambda<Func<T, bool>>(

        Expression.AndAlso(

            expr1.Body,

            Expression.Invoke(expr2, param)), param);

}

Starting from .net 4.0. There is the ExpressionVistor class which allows you to build expressions that are EF safe.

    public static Expression<Func<T, bool>> AndAlso<T>(

        this Expression<Func<T, bool>> expr1,

        Expression<Func<T, bool>> expr2)

    {

        var parameter = Expression.Parameter(typeof (T));



        var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);

        var left = leftVisitor.Visit(expr1.Body);



        var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);

        var right = rightVisitor.Visit(expr2.Body);



        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(left, right), parameter);

    }







    private class ReplaceExpressionVisitor

        : ExpressionVisitor

    {

        private readonly Expression _oldValue;

        private readonly Expression _newValue;



        public ReplaceExpressionVisitor(Expression oldValue, Expression newValue)

        {

            _oldValue = oldValue;

            _newValue = newValue;

        }



        public override Expression Visit(Expression node)

        {

            if (node == _oldValue)

                return _newValue;

            return base.Visit(node);

        }

    }

edited Feb 27 '15 at 10:55

user3934443

answered Jan 19 '09 at 11:32

Marc Gravell♦

777k19221262539

var body = Expression.AndAlso(expr1.Body, expr2.Body);

var lambda = Expression.Lambda<Func<T,bool>>(body, expr1.Parameters[0]);

This also works well to negate a single operation:

static Expression<Func<T, bool>> Not<T>(

    this Expression<Func<T, bool>> expr)

{

    return Expression.Lambda<Func<T, bool>>(

        Expression.Not(expr.Body), expr.Parameters[0]);

}

Otherwise, depending on the LINQ provider, you might be able to combine them with Invoke:

// OrElse is very similar...

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> left,

    Expression<Func<T, bool>> right)

{

    var param = Expression.Parameter(typeof(T), "x");

    var body = Expression.AndAlso(

            Expression.Invoke(left, param),

            Expression.Invoke(right, param)

        );

    var lambda = Expression.Lambda<Func<T, bool>>(body, param);

    return lambda;

}

Somewhere, I have got some code that re-writes an expression-tree replacing nodes to remove the need for Invoke, but it is quite lengthy (and I can't remember where I left it...)

Generalized version that picks the simplest route:

static Expression<Func<T, bool>> AndAlso<T>(

    this Expression<Func<T, bool>> expr1,

    Expression<Func<T, bool>> expr2)

{

    // need to detect whether they use the same

    // parameter instance; if not, they need fixing

    ParameterExpression param = expr1.Parameters[0];

    if (ReferenceEquals(param, expr2.Parameters[0]))

    {

        // simple version

        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(expr1.Body, expr2.Body), param);

    }

    // otherwise, keep expr1 "as is" and invoke expr2

    return Expression.Lambda<Func<T, bool>>(

        Expression.AndAlso(

            expr1.Body,

            Expression.Invoke(expr2, param)), param);

}

Starting from .net 4.0. There is the ExpressionVistor class which allows you to build expressions that are EF safe.

    public static Expression<Func<T, bool>> AndAlso<T>(

        this Expression<Func<T, bool>> expr1,

        Expression<Func<T, bool>> expr2)

    {

        var parameter = Expression.Parameter(typeof (T));



        var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);

        var left = leftVisitor.Visit(expr1.Body);



        var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);

        var right = rightVisitor.Visit(expr2.Body);



        return Expression.Lambda<Func<T, bool>>(

            Expression.AndAlso(left, right), parameter);

    }







    private class ReplaceExpressionVisitor

        : ExpressionVisitor

    {

        private readonly Expression _oldValue;

        private readonly Expression _newValue;



        public ReplaceExpressionVisitor(Expression oldValue, Expression newValue)

        {

            _oldValue = oldValue;

            _newValue = newValue;

        }



        public override Expression Visit(Expression node)

        {

            if (node == _oldValue)

                return _newValue;

            return base.Visit(node);

        }

    }

edited Feb 27 '15 at 10:55

user3934443

answered Jan 19 '09 at 11:32

Marc Gravell♦

777k19221262539

edited Feb 27 '15 at 10:55

user3934443

edited Feb 27 '15 at 10:55

user3934443

edited Feb 27 '15 at 10:55

user3934443

answered Jan 19 '09 at 11:32

Marc Gravell♦

777k19221262539

answered Jan 19 '09 at 11:32

Marc Gravell♦

777k19221262539

answered Jan 19 '09 at 11:32

Marc Gravell♦

777k19221262539

Hey Marc, I tried out your first suggestion, in the your first code block above, but when I pass in the "lambda" expression<func<T,bool>> result in a Where method, I get an error saying the parameter is out of scope? any idea? cheers
– andy
Jun 27 '09 at 5:52

1

+1 the generalized version works like a charm, I used And instead of andalso, I thought linq to sql doesn't support andalso?
– Maslow
Sep 4 '09 at 13:57

2

@Maslow - here's a rewriter that can inline the trees to save Invoke: stackoverflow.com/questions/1717444/…
– Marc Gravell♦
Mar 19 '11 at 21:12

1

@Aron now look at the date: the .NET framework visitor (ExpressionVisitor) did not exist back then; I have a related example on stackoverflow from a similar date where it implements the visitor manually: it is a lot of code.
– Marc Gravell♦
Aug 13 '14 at 7:09

1

@MarkGravell, I'm using your first solution to combine my expressions, and everything is working fine even in entityframework, So what would the benefits of using the last solution be?
– johnny 5
Aug 3 '17 at 0:08

|
show 16 more comments

Hey Marc, I tried out your first suggestion, in the your first code block above, but when I pass in the "lambda" expression<func<T,bool>> result in a Where method, I get an error saying the parameter is out of scope? any idea? cheers
– andy
Jun 27 '09 at 5:52

1

+1 the generalized version works like a charm, I used And instead of andalso, I thought linq to sql doesn't support andalso?
– Maslow
Sep 4 '09 at 13:57

2

@Maslow - here's a rewriter that can inline the trees to save Invoke: stackoverflow.com/questions/1717444/…
– Marc Gravell♦
Mar 19 '11 at 21:12

1

@Aron now look at the date: the .NET framework visitor (ExpressionVisitor) did not exist back then; I have a related example on stackoverflow from a similar date where it implements the visitor manually: it is a lot of code.
– Marc Gravell♦
Aug 13 '14 at 7:09

1

@MarkGravell, I'm using your first solution to combine my expressions, and everything is working fine even in entityframework, So what would the benefits of using the last solution be?
– johnny 5
Aug 3 '17 at 0:08

Hey Marc, I tried out your first suggestion, in the your first code block above, but when I pass in the "lambda" expression<func<T,bool>> result in a Where method, I get an error saying the parameter is out of scope? any idea? cheers
– andy
Jun 27 '09 at 5:52

+1 the generalized version works like a charm, I used And instead of andalso, I thought linq to sql doesn't support andalso?
– Maslow
Sep 4 '09 at 13:57

@Maslow - here's a rewriter that can inline the trees to save Invoke: stackoverflow.com/questions/1717444/…
– Marc Gravell♦
Mar 19 '11 at 21:12

@Aron now look at the date: the .NET framework visitor (ExpressionVisitor) did not exist back then; I have a related example on stackoverflow from a similar date where it implements the visitor manually: it is a lot of code.
– Marc Gravell♦
Aug 13 '14 at 7:09

@MarkGravell, I'm using your first solution to combine my expressions, and everything is working fine even in entityframework, So what would the benefits of using the last solution be?
– johnny 5
Aug 3 '17 at 0:08

|
show 16 more comments

You can use Expression.AndAlso / OrElse to combine logical expressions, but you have to make sure the ParameterExpressions are the same.

I was having trouble with EF and the PredicateBuilder so I made my own without resorting to Invoke, that I could use like this:

var filterC = filterA.And(filterb);

Source code for my PredicateBuilder:

public static class PredicateBuilder {



    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.AndAlso(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }



    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.OrElse(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }   

}

And the utility class to substitute the parameters in a lambda:

internal class SubstExpressionVisitor : System.Linq.Expressions.ExpressionVisitor {

        public Dictionary<Expression, Expression> subst = new Dictionary<Expression, Expression>();



        protected override Expression VisitParameter(ParameterExpression node) {

            Expression newValue;

            if (subst.TryGetValue(node, out newValue)) {

                return newValue;

            }

            return node;

        }

    }

answered Sep 19 '12 at 14:53

Adam Tegen

13.8k30109145

This solution was the only one that allowed me to have x => x.Property == Value combined with arg => arg.Property2 == Value. Major props, a little terse and confusing but it works so I'm not going to complain. Kudos Adam :-)
– VulgarBinary
Dec 12 '12 at 20:38

Thanks. I've found the code useful in a lot of places.
– Adam Tegen
Dec 13 '12 at 19:10

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:26

Adam, this solved a very annoying problem I was having using the SharePoint Client Object model's Linq provider - thanks for posting it.
– Christopher McAtackney
Jul 9 '14 at 14:30

This worked for me! I had searched for a variety of solutions as well as predicate builder and nothing worked until this. Thank you!
– tokyo0709
Aug 1 '16 at 20:10

|
show 1 more comment

You can use Expression.AndAlso / OrElse to combine logical expressions, but you have to make sure the ParameterExpressions are the same.

I was having trouble with EF and the PredicateBuilder so I made my own without resorting to Invoke, that I could use like this:

var filterC = filterA.And(filterb);

Source code for my PredicateBuilder:

public static class PredicateBuilder {



    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.AndAlso(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }



    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.OrElse(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }   

}

And the utility class to substitute the parameters in a lambda:

internal class SubstExpressionVisitor : System.Linq.Expressions.ExpressionVisitor {

        public Dictionary<Expression, Expression> subst = new Dictionary<Expression, Expression>();



        protected override Expression VisitParameter(ParameterExpression node) {

            Expression newValue;

            if (subst.TryGetValue(node, out newValue)) {

                return newValue;

            }

            return node;

        }

    }

answered Sep 19 '12 at 14:53

Adam Tegen

13.8k30109145

This solution was the only one that allowed me to have x => x.Property == Value combined with arg => arg.Property2 == Value. Major props, a little terse and confusing but it works so I'm not going to complain. Kudos Adam :-)
– VulgarBinary
Dec 12 '12 at 20:38

Thanks. I've found the code useful in a lot of places.
– Adam Tegen
Dec 13 '12 at 19:10

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:26

Adam, this solved a very annoying problem I was having using the SharePoint Client Object model's Linq provider - thanks for posting it.
– Christopher McAtackney
Jul 9 '14 at 14:30

This worked for me! I had searched for a variety of solutions as well as predicate builder and nothing worked until this. Thank you!
– tokyo0709
Aug 1 '16 at 20:10

|
show 1 more comment

You can use Expression.AndAlso / OrElse to combine logical expressions, but you have to make sure the ParameterExpressions are the same.

I was having trouble with EF and the PredicateBuilder so I made my own without resorting to Invoke, that I could use like this:

var filterC = filterA.And(filterb);

Source code for my PredicateBuilder:

public static class PredicateBuilder {



    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.AndAlso(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }



    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.OrElse(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }   

}

And the utility class to substitute the parameters in a lambda:

internal class SubstExpressionVisitor : System.Linq.Expressions.ExpressionVisitor {

        public Dictionary<Expression, Expression> subst = new Dictionary<Expression, Expression>();



        protected override Expression VisitParameter(ParameterExpression node) {

            Expression newValue;

            if (subst.TryGetValue(node, out newValue)) {

                return newValue;

            }

            return node;

        }

    }

answered Sep 19 '12 at 14:53

Adam Tegen

13.8k30109145

You can use Expression.AndAlso / OrElse to combine logical expressions, but you have to make sure the ParameterExpressions are the same.

I was having trouble with EF and the PredicateBuilder so I made my own without resorting to Invoke, that I could use like this:

var filterC = filterA.And(filterb);

Source code for my PredicateBuilder:

public static class PredicateBuilder {



    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.AndAlso(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }



    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b) {    



        ParameterExpression p = a.Parameters[0];



        SubstExpressionVisitor visitor = new SubstExpressionVisitor();

        visitor.subst[b.Parameters[0]] = p;



        Expression body = Expression.OrElse(a.Body, visitor.Visit(b.Body));

        return Expression.Lambda<Func<T, bool>>(body, p);

    }   

}

And the utility class to substitute the parameters in a lambda:

internal class SubstExpressionVisitor : System.Linq.Expressions.ExpressionVisitor {

        public Dictionary<Expression, Expression> subst = new Dictionary<Expression, Expression>();



        protected override Expression VisitParameter(ParameterExpression node) {

            Expression newValue;

            if (subst.TryGetValue(node, out newValue)) {

                return newValue;

            }

            return node;

        }

    }

answered Sep 19 '12 at 14:53

Adam Tegen

13.8k30109145

answered Sep 19 '12 at 14:53

Adam Tegen

13.8k30109145

answered Sep 19 '12 at 14:53

Adam Tegen

13.8k30109145

answered Sep 19 '12 at 14:53

Adam Tegen

13.8k30109145

This solution was the only one that allowed me to have x => x.Property == Value combined with arg => arg.Property2 == Value. Major props, a little terse and confusing but it works so I'm not going to complain. Kudos Adam :-)
– VulgarBinary
Dec 12 '12 at 20:38

Thanks. I've found the code useful in a lot of places.
– Adam Tegen
Dec 13 '12 at 19:10

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:26

Adam, this solved a very annoying problem I was having using the SharePoint Client Object model's Linq provider - thanks for posting it.
– Christopher McAtackney
Jul 9 '14 at 14:30

This worked for me! I had searched for a variety of solutions as well as predicate builder and nothing worked until this. Thank you!
– tokyo0709
Aug 1 '16 at 20:10

|
show 1 more comment

This solution was the only one that allowed me to have x => x.Property == Value combined with arg => arg.Property2 == Value. Major props, a little terse and confusing but it works so I'm not going to complain. Kudos Adam :-)
– VulgarBinary
Dec 12 '12 at 20:38

Thanks. I've found the code useful in a lot of places.
– Adam Tegen
Dec 13 '12 at 19:10

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:26

Adam, this solved a very annoying problem I was having using the SharePoint Client Object model's Linq provider - thanks for posting it.
– Christopher McAtackney
Jul 9 '14 at 14:30

This worked for me! I had searched for a variety of solutions as well as predicate builder and nothing worked until this. Thank you!
– tokyo0709
Aug 1 '16 at 20:10

This solution was the only one that allowed me to have x => x.Property == Value combined with arg => arg.Property2 == Value. Major props, a little terse and confusing but it works so I'm not going to complain. Kudos Adam :-)
– VulgarBinary
Dec 12 '12 at 20:38

Thanks. I've found the code useful in a lot of places.
– Adam Tegen
Dec 13 '12 at 19:10

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:26

Adam, this solved a very annoying problem I was having using the SharePoint Client Object model's Linq provider - thanks for posting it.
– Christopher McAtackney
Jul 9 '14 at 14:30

This worked for me! I had searched for a variety of solutions as well as predicate builder and nothing worked until this. Thank you!
– tokyo0709
Aug 1 '16 at 20:10

|
show 1 more comment

Joe Albahari (Author of C# 3.0 in a Nutshell and LINQPad) wrote a utility called PredicateBuilder which can be used to AND and OR functions together.

http://www.albahari.com/nutshell/predicatebuilder.aspx

While it works on functions it is open source so you can check it out and see how it works.

answered Jan 19 '09 at 22:52

Cameron MacFarland

52.2k1892120

1

The best solution!! The choosen answer is not as clear as the PredicatedBuilder solution. +1 for that!
– Eduardo Xavier
Oct 17 '11 at 16:51

@Eduardo: I disagree. PredicateBuilder's code is largely identical to the chosen answer, but the chosen answer provides explanation/code directly instead of via link.
– Brian
Mar 30 '12 at 15:37

4

PredicateBuilder DOES NOT WORK IN EF!!!!!!!!!!!!!!! It evaluates the query from the server then applies the desired predicate in memory instead of passing the predicate to SQL to restrict the result set. This is why PredicateBuilder is not desirable for this use case! BUYER BEWARE
– VulgarBinary
Dec 12 '12 at 20:40

@VulgarBinary Perhaps you could spend some time figuring out why it doesn't work in EF5 instead of waiting for the answer to be spoon-fed to you.
– Cameron MacFarland
Dec 13 '12 at 0:39

1

@CameronMacFarland I had already written a new PredicateBuilder myself that works and optimizes the expression trees. This snippet gave me the last piece I needed which was the visitor component. I was hardly waiting for anything to be spoon fed, if you seriously want your points back that badly edit your response and I'll take back the -1. However, when someone is looking to do something with Expression<Func<T,bool>> it generally means they want to use EF. Otherwise they would just have used Func<T,bool>
– VulgarBinary
Dec 13 '12 at 1:01

|
show 3 more comments

Joe Albahari (Author of C# 3.0 in a Nutshell and LINQPad) wrote a utility called PredicateBuilder which can be used to AND and OR functions together.

http://www.albahari.com/nutshell/predicatebuilder.aspx

While it works on functions it is open source so you can check it out and see how it works.

answered Jan 19 '09 at 22:52

Cameron MacFarland

52.2k1892120

1

The best solution!! The choosen answer is not as clear as the PredicatedBuilder solution. +1 for that!
– Eduardo Xavier
Oct 17 '11 at 16:51

@Eduardo: I disagree. PredicateBuilder's code is largely identical to the chosen answer, but the chosen answer provides explanation/code directly instead of via link.
– Brian
Mar 30 '12 at 15:37

4

PredicateBuilder DOES NOT WORK IN EF!!!!!!!!!!!!!!! It evaluates the query from the server then applies the desired predicate in memory instead of passing the predicate to SQL to restrict the result set. This is why PredicateBuilder is not desirable for this use case! BUYER BEWARE
– VulgarBinary
Dec 12 '12 at 20:40

@VulgarBinary Perhaps you could spend some time figuring out why it doesn't work in EF5 instead of waiting for the answer to be spoon-fed to you.
– Cameron MacFarland
Dec 13 '12 at 0:39

1

@CameronMacFarland I had already written a new PredicateBuilder myself that works and optimizes the expression trees. This snippet gave me the last piece I needed which was the visitor component. I was hardly waiting for anything to be spoon fed, if you seriously want your points back that badly edit your response and I'll take back the -1. However, when someone is looking to do something with Expression<Func<T,bool>> it generally means they want to use EF. Otherwise they would just have used Func<T,bool>
– VulgarBinary
Dec 13 '12 at 1:01

|
show 3 more comments

Joe Albahari (Author of C# 3.0 in a Nutshell and LINQPad) wrote a utility called PredicateBuilder which can be used to AND and OR functions together.

http://www.albahari.com/nutshell/predicatebuilder.aspx

While it works on functions it is open source so you can check it out and see how it works.

answered Jan 19 '09 at 22:52

Cameron MacFarland

52.2k1892120

Joe Albahari (Author of C# 3.0 in a Nutshell and LINQPad) wrote a utility called PredicateBuilder which can be used to AND and OR functions together.

http://www.albahari.com/nutshell/predicatebuilder.aspx

While it works on functions it is open source so you can check it out and see how it works.

answered Jan 19 '09 at 22:52

Cameron MacFarland

52.2k1892120

answered Jan 19 '09 at 22:52

Cameron MacFarland

52.2k1892120

answered Jan 19 '09 at 22:52

Cameron MacFarland

52.2k1892120

answered Jan 19 '09 at 22:52

Cameron MacFarland

52.2k1892120

1

The best solution!! The choosen answer is not as clear as the PredicatedBuilder solution. +1 for that!
– Eduardo Xavier
Oct 17 '11 at 16:51

@Eduardo: I disagree. PredicateBuilder's code is largely identical to the chosen answer, but the chosen answer provides explanation/code directly instead of via link.
– Brian
Mar 30 '12 at 15:37

4

PredicateBuilder DOES NOT WORK IN EF!!!!!!!!!!!!!!! It evaluates the query from the server then applies the desired predicate in memory instead of passing the predicate to SQL to restrict the result set. This is why PredicateBuilder is not desirable for this use case! BUYER BEWARE
– VulgarBinary
Dec 12 '12 at 20:40

@VulgarBinary Perhaps you could spend some time figuring out why it doesn't work in EF5 instead of waiting for the answer to be spoon-fed to you.
– Cameron MacFarland
Dec 13 '12 at 0:39

1

@CameronMacFarland I had already written a new PredicateBuilder myself that works and optimizes the expression trees. This snippet gave me the last piece I needed which was the visitor component. I was hardly waiting for anything to be spoon fed, if you seriously want your points back that badly edit your response and I'll take back the -1. However, when someone is looking to do something with Expression<Func<T,bool>> it generally means they want to use EF. Otherwise they would just have used Func<T,bool>
– VulgarBinary
Dec 13 '12 at 1:01

|
show 3 more comments

1

The best solution!! The choosen answer is not as clear as the PredicatedBuilder solution. +1 for that!
– Eduardo Xavier
Oct 17 '11 at 16:51

@Eduardo: I disagree. PredicateBuilder's code is largely identical to the chosen answer, but the chosen answer provides explanation/code directly instead of via link.
– Brian
Mar 30 '12 at 15:37

4

PredicateBuilder DOES NOT WORK IN EF!!!!!!!!!!!!!!! It evaluates the query from the server then applies the desired predicate in memory instead of passing the predicate to SQL to restrict the result set. This is why PredicateBuilder is not desirable for this use case! BUYER BEWARE
– VulgarBinary
Dec 12 '12 at 20:40

@VulgarBinary Perhaps you could spend some time figuring out why it doesn't work in EF5 instead of waiting for the answer to be spoon-fed to you.
– Cameron MacFarland
Dec 13 '12 at 0:39

1

@CameronMacFarland I had already written a new PredicateBuilder myself that works and optimizes the expression trees. This snippet gave me the last piece I needed which was the visitor component. I was hardly waiting for anything to be spoon fed, if you seriously want your points back that badly edit your response and I'll take back the -1. However, when someone is looking to do something with Expression<Func<T,bool>> it generally means they want to use EF. Otherwise they would just have used Func<T,bool>
– VulgarBinary
Dec 13 '12 at 1:01

The best solution!! The choosen answer is not as clear as the PredicatedBuilder solution. +1 for that!
– Eduardo Xavier
Oct 17 '11 at 16:51

@Eduardo: I disagree. PredicateBuilder's code is largely identical to the chosen answer, but the chosen answer provides explanation/code directly instead of via link.
– Brian
Mar 30 '12 at 15:37

PredicateBuilder DOES NOT WORK IN EF!!!!!!!!!!!!!!! It evaluates the query from the server then applies the desired predicate in memory instead of passing the predicate to SQL to restrict the result set. This is why PredicateBuilder is not desirable for this use case! BUYER BEWARE
– VulgarBinary
Dec 12 '12 at 20:40

@VulgarBinary Perhaps you could spend some time figuring out why it doesn't work in EF5 instead of waiting for the answer to be spoon-fed to you.
– Cameron MacFarland
Dec 13 '12 at 0:39

@CameronMacFarland I had already written a new PredicateBuilder myself that works and optimizes the expression trees. This snippet gave me the last piece I needed which was the visitor component. I was hardly waiting for anything to be spoon fed, if you seriously want your points back that badly edit your response and I'll take back the -1. However, when someone is looking to do something with Expression<Func<T,bool>> it generally means they want to use EF. Otherwise they would just have used Func<T,bool>
– VulgarBinary
Dec 13 '12 at 1:01

|
show 3 more comments

class ParameterUpdateVisitor : ExpressionVisitor

{

    private ParameterExpression _oldParameter;

    private ParameterExpression _newParameter;



    public ParameterUpdateVisitor(ParameterExpression oldParameter, ParameterExpression newParameter)

    {

        _oldParameter = oldParameter;

        _newParameter = newParameter;

    }



    protected override Expression VisitParameter(ParameterExpression node)

    {

        if (object.ReferenceEquals(node, _oldParameter))

            return _newParameter;



        return base.VisitParameter(node);

    }

}



static Expression<Func<T, bool>> UpdateParameter<T>(

    Expression<Func<T, bool>> expr,

    ParameterExpression newParameter)

{

    var visitor = new ParameterUpdateVisitor(expr.Parameters[0], newParameter);

    var body = visitor.Visit(expr.Body);



    return Expression.Lambda<Func<T, bool>>(body, newParameter);

}



[TestMethod]

public void ExpressionText()

{

    string text = "test";



    Expression<Func<Coco, bool>> expr1 = p => p.Item1.Contains(text);

    Expression<Func<Coco, bool>> expr2 = q => q.Item2.Contains(text);

    Expression<Func<Coco, bool>> expr3 = UpdateParameter(expr2, expr1.Parameters[0]);



    var expr4 = Expression.Lambda<Func<Recording, bool>>(

        Expression.OrElse(expr1.Body, expr3.Body), expr1.Parameters[0]);



    var func = expr4.Compile();



    Assert.IsTrue(func(new Coco { Item1 = "caca", Item2 = "test pipi" }));

}

edited Dec 13 '12 at 15:18

answered Dec 15 '11 at 15:36

Francis

2,7371243

1

This solved my particular problem where the other solution resulted in the same exception. Thanks.
– Shaun Wilson
Mar 7 '13 at 23:49

1

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:25

add a comment |

class ParameterUpdateVisitor : ExpressionVisitor

{

    private ParameterExpression _oldParameter;

    private ParameterExpression _newParameter;



    public ParameterUpdateVisitor(ParameterExpression oldParameter, ParameterExpression newParameter)

    {

        _oldParameter = oldParameter;

        _newParameter = newParameter;

    }



    protected override Expression VisitParameter(ParameterExpression node)

    {

        if (object.ReferenceEquals(node, _oldParameter))

            return _newParameter;



        return base.VisitParameter(node);

    }

}



static Expression<Func<T, bool>> UpdateParameter<T>(

    Expression<Func<T, bool>> expr,

    ParameterExpression newParameter)

{

    var visitor = new ParameterUpdateVisitor(expr.Parameters[0], newParameter);

    var body = visitor.Visit(expr.Body);



    return Expression.Lambda<Func<T, bool>>(body, newParameter);

}



[TestMethod]

public void ExpressionText()

{

    string text = "test";



    Expression<Func<Coco, bool>> expr1 = p => p.Item1.Contains(text);

    Expression<Func<Coco, bool>> expr2 = q => q.Item2.Contains(text);

    Expression<Func<Coco, bool>> expr3 = UpdateParameter(expr2, expr1.Parameters[0]);



    var expr4 = Expression.Lambda<Func<Recording, bool>>(

        Expression.OrElse(expr1.Body, expr3.Body), expr1.Parameters[0]);



    var func = expr4.Compile();



    Assert.IsTrue(func(new Coco { Item1 = "caca", Item2 = "test pipi" }));

}

edited Dec 13 '12 at 15:18

answered Dec 15 '11 at 15:36

Francis

2,7371243

1

This solved my particular problem where the other solution resulted in the same exception. Thanks.
– Shaun Wilson
Mar 7 '13 at 23:49

1

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:25

add a comment |

class ParameterUpdateVisitor : ExpressionVisitor

{

    private ParameterExpression _oldParameter;

    private ParameterExpression _newParameter;



    public ParameterUpdateVisitor(ParameterExpression oldParameter, ParameterExpression newParameter)

    {

        _oldParameter = oldParameter;

        _newParameter = newParameter;

    }



    protected override Expression VisitParameter(ParameterExpression node)

    {

        if (object.ReferenceEquals(node, _oldParameter))

            return _newParameter;



        return base.VisitParameter(node);

    }

}



static Expression<Func<T, bool>> UpdateParameter<T>(

    Expression<Func<T, bool>> expr,

    ParameterExpression newParameter)

{

    var visitor = new ParameterUpdateVisitor(expr.Parameters[0], newParameter);

    var body = visitor.Visit(expr.Body);



    return Expression.Lambda<Func<T, bool>>(body, newParameter);

}



[TestMethod]

public void ExpressionText()

{

    string text = "test";



    Expression<Func<Coco, bool>> expr1 = p => p.Item1.Contains(text);

    Expression<Func<Coco, bool>> expr2 = q => q.Item2.Contains(text);

    Expression<Func<Coco, bool>> expr3 = UpdateParameter(expr2, expr1.Parameters[0]);



    var expr4 = Expression.Lambda<Func<Recording, bool>>(

        Expression.OrElse(expr1.Body, expr3.Body), expr1.Parameters[0]);



    var func = expr4.Compile();



    Assert.IsTrue(func(new Coco { Item1 = "caca", Item2 = "test pipi" }));

}

edited Dec 13 '12 at 15:18

answered Dec 15 '11 at 15:36

Francis

2,7371243

class ParameterUpdateVisitor : ExpressionVisitor

{

    private ParameterExpression _oldParameter;

    private ParameterExpression _newParameter;



    public ParameterUpdateVisitor(ParameterExpression oldParameter, ParameterExpression newParameter)

    {

        _oldParameter = oldParameter;

        _newParameter = newParameter;

    }



    protected override Expression VisitParameter(ParameterExpression node)

    {

        if (object.ReferenceEquals(node, _oldParameter))

            return _newParameter;



        return base.VisitParameter(node);

    }

}



static Expression<Func<T, bool>> UpdateParameter<T>(

    Expression<Func<T, bool>> expr,

    ParameterExpression newParameter)

{

    var visitor = new ParameterUpdateVisitor(expr.Parameters[0], newParameter);

    var body = visitor.Visit(expr.Body);



    return Expression.Lambda<Func<T, bool>>(body, newParameter);

}



[TestMethod]

public void ExpressionText()

{

    string text = "test";



    Expression<Func<Coco, bool>> expr1 = p => p.Item1.Contains(text);

    Expression<Func<Coco, bool>> expr2 = q => q.Item2.Contains(text);

    Expression<Func<Coco, bool>> expr3 = UpdateParameter(expr2, expr1.Parameters[0]);



    var expr4 = Expression.Lambda<Func<Recording, bool>>(

        Expression.OrElse(expr1.Body, expr3.Body), expr1.Parameters[0]);



    var func = expr4.Compile();



    Assert.IsTrue(func(new Coco { Item1 = "caca", Item2 = "test pipi" }));

}

edited Dec 13 '12 at 15:18

answered Dec 15 '11 at 15:36

Francis

2,7371243

edited Dec 13 '12 at 15:18

answered Dec 15 '11 at 15:36

Francis

2,7371243

answered Dec 15 '11 at 15:36

Francis

2,7371243

answered Dec 15 '11 at 15:36

Francis

2,7371243

1

This solved my particular problem where the other solution resulted in the same exception. Thanks.
– Shaun Wilson
Mar 7 '13 at 23:49

1

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:25

add a comment |

1

This solved my particular problem where the other solution resulted in the same exception. Thanks.
– Shaun Wilson
Mar 7 '13 at 23:49

1

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:25

This solved my particular problem where the other solution resulted in the same exception. Thanks.
– Shaun Wilson
Mar 7 '13 at 23:49

This is a great solution.
– Aaron Stainback
May 13 '14 at 23:25

add a comment |

public IQueryable<UbezpExt> UbezpFull

{

    get

    {

        System.Linq.Expressions.Expression<

            Func<UBEZPIECZONY, UBEZP_ADRES, UBEZP_ADRES, UbezpExt>> expr =

            (u, parAdrM, parAdrZ) => new UbezpExt

            {

                Ub = u,

                AdrM = parAdrM,

                AdrZ = parAdrZ,

            };



        // From here an expression builder ExprAdres is called.

        var expr2 = expr

            .ReplacePar("parAdrM", ExprAdres("M").Body)

            .ReplacePar("parAdrZ", ExprAdres("Z").Body);

        return UBEZPIECZONY.Select((Expression<Func<UBEZPIECZONY, UbezpExt>>)expr2);

    }

}

And this is the subexpression building code:

public static Expression<Func<UBEZPIECZONY, UBEZP_ADRES>> ExprAdres(string sTyp)

{

    return u => u.UBEZP_ADRES.Where(a => a.TYP_ADRESU == sTyp)

        .OrderByDescending(a => a.DATAOD).FirstOrDefault();

}

answered Oct 16 '16 at 20:46

Jarekczek

5,01913050

add a comment |

public IQueryable<UbezpExt> UbezpFull

{

    get

    {

        System.Linq.Expressions.Expression<

            Func<UBEZPIECZONY, UBEZP_ADRES, UBEZP_ADRES, UbezpExt>> expr =

            (u, parAdrM, parAdrZ) => new UbezpExt

            {

                Ub = u,

                AdrM = parAdrM,

                AdrZ = parAdrZ,

            };



        // From here an expression builder ExprAdres is called.

        var expr2 = expr

            .ReplacePar("parAdrM", ExprAdres("M").Body)

            .ReplacePar("parAdrZ", ExprAdres("Z").Body);

        return UBEZPIECZONY.Select((Expression<Func<UBEZPIECZONY, UbezpExt>>)expr2);

    }

}

And this is the subexpression building code:

public static Expression<Func<UBEZPIECZONY, UBEZP_ADRES>> ExprAdres(string sTyp)

{

    return u => u.UBEZP_ADRES.Where(a => a.TYP_ADRESU == sTyp)

        .OrderByDescending(a => a.DATAOD).FirstOrDefault();

}

answered Oct 16 '16 at 20:46

Jarekczek

5,01913050

add a comment |

public IQueryable<UbezpExt> UbezpFull

{

    get

    {

        System.Linq.Expressions.Expression<

            Func<UBEZPIECZONY, UBEZP_ADRES, UBEZP_ADRES, UbezpExt>> expr =

            (u, parAdrM, parAdrZ) => new UbezpExt

            {

                Ub = u,

                AdrM = parAdrM,

                AdrZ = parAdrZ,

            };



        // From here an expression builder ExprAdres is called.

        var expr2 = expr

            .ReplacePar("parAdrM", ExprAdres("M").Body)

            .ReplacePar("parAdrZ", ExprAdres("Z").Body);

        return UBEZPIECZONY.Select((Expression<Func<UBEZPIECZONY, UbezpExt>>)expr2);

    }

}

And this is the subexpression building code:

public static Expression<Func<UBEZPIECZONY, UBEZP_ADRES>> ExprAdres(string sTyp)

{

    return u => u.UBEZP_ADRES.Where(a => a.TYP_ADRESU == sTyp)

        .OrderByDescending(a => a.DATAOD).FirstOrDefault();

}

answered Oct 16 '16 at 20:46

Jarekczek

5,01913050

public IQueryable<UbezpExt> UbezpFull

{

    get

    {

        System.Linq.Expressions.Expression<

            Func<UBEZPIECZONY, UBEZP_ADRES, UBEZP_ADRES, UbezpExt>> expr =

            (u, parAdrM, parAdrZ) => new UbezpExt

            {

                Ub = u,

                AdrM = parAdrM,

                AdrZ = parAdrZ,

            };



        // From here an expression builder ExprAdres is called.

        var expr2 = expr

            .ReplacePar("parAdrM", ExprAdres("M").Body)

            .ReplacePar("parAdrZ", ExprAdres("Z").Body);

        return UBEZPIECZONY.Select((Expression<Func<UBEZPIECZONY, UbezpExt>>)expr2);

    }

}

And this is the subexpression building code:

public static Expression<Func<UBEZPIECZONY, UBEZP_ADRES>> ExprAdres(string sTyp)

{

    return u => u.UBEZP_ADRES.Where(a => a.TYP_ADRESU == sTyp)

        .OrderByDescending(a => a.DATAOD).FirstOrDefault();

}

answered Oct 16 '16 at 20:46

Jarekczek

5,01913050

answered Oct 16 '16 at 20:46

Jarekczek

5,01913050

answered Oct 16 '16 at 20:46

Jarekczek

5,01913050

answered Oct 16 '16 at 20:46

Jarekczek

5,01913050

add a comment |

I needed to achieve the same results, but using something more generic (as the type was not known). Thanks to marc's answer I finally figured out what I was trying to achieve:

    public static LambdaExpression CombineOr(Type sourceType, LambdaExpression exp, LambdaExpression newExp) 

    {

        var parameter = Expression.Parameter(sourceType);



        var leftVisitor = new ReplaceExpressionVisitor(exp.Parameters[0], parameter);

        var left = leftVisitor.Visit(exp.Body);



        var rightVisitor = new ReplaceExpressionVisitor(newExp.Parameters[0], parameter);

        var right = rightVisitor.Visit(newExp.Body);



        var delegateType = typeof(Func<,>).MakeGenericType(sourceType, typeof(bool));

        return Expression.Lambda(delegateType, Expression.Or(left, right), parameter);

    }

answered Jun 1 '17 at 12:48

VorTechS

171210

add a comment |

I needed to achieve the same results, but using something more generic (as the type was not known). Thanks to marc's answer I finally figured out what I was trying to achieve:

    public static LambdaExpression CombineOr(Type sourceType, LambdaExpression exp, LambdaExpression newExp) 

    {

        var parameter = Expression.Parameter(sourceType);



        var leftVisitor = new ReplaceExpressionVisitor(exp.Parameters[0], parameter);

        var left = leftVisitor.Visit(exp.Body);



        var rightVisitor = new ReplaceExpressionVisitor(newExp.Parameters[0], parameter);

        var right = rightVisitor.Visit(newExp.Body);



        var delegateType = typeof(Func<,>).MakeGenericType(sourceType, typeof(bool));

        return Expression.Lambda(delegateType, Expression.Or(left, right), parameter);

    }

answered Jun 1 '17 at 12:48

VorTechS

171210

add a comment |

I needed to achieve the same results, but using something more generic (as the type was not known). Thanks to marc's answer I finally figured out what I was trying to achieve:

    public static LambdaExpression CombineOr(Type sourceType, LambdaExpression exp, LambdaExpression newExp) 

    {

        var parameter = Expression.Parameter(sourceType);



        var leftVisitor = new ReplaceExpressionVisitor(exp.Parameters[0], parameter);

        var left = leftVisitor.Visit(exp.Body);



        var rightVisitor = new ReplaceExpressionVisitor(newExp.Parameters[0], parameter);

        var right = rightVisitor.Visit(newExp.Body);



        var delegateType = typeof(Func<,>).MakeGenericType(sourceType, typeof(bool));

        return Expression.Lambda(delegateType, Expression.Or(left, right), parameter);

    }

answered Jun 1 '17 at 12:48

VorTechS

171210

I needed to achieve the same results, but using something more generic (as the type was not known). Thanks to marc's answer I finally figured out what I was trying to achieve:

    public static LambdaExpression CombineOr(Type sourceType, LambdaExpression exp, LambdaExpression newExp) 

    {

        var parameter = Expression.Parameter(sourceType);



        var leftVisitor = new ReplaceExpressionVisitor(exp.Parameters[0], parameter);

        var left = leftVisitor.Visit(exp.Body);



        var rightVisitor = new ReplaceExpressionVisitor(newExp.Parameters[0], parameter);

        var right = rightVisitor.Visit(newExp.Body);



        var delegateType = typeof(Func<,>).MakeGenericType(sourceType, typeof(bool));

        return Expression.Lambda(delegateType, Expression.Or(left, right), parameter);

    }

answered Jun 1 '17 at 12:48

VorTechS

171210

answered Jun 1 '17 at 12:48

VorTechS

171210

answered Jun 1 '17 at 12:48

VorTechS

171210

answered Jun 1 '17 at 12:48

VorTechS

171210

add a comment |

-7

I think this works fine, isn't it ?

Func<T, bool> expr1 = (x => x.Att1 == "a");

Func<T, bool> expr2 = (x => x.Att2 == "b");

Func<T, bool> expr1ANDexpr2 = (x => expr1(x) && expr2(x));

Func<T, bool> expr1ORexpr2 = (x => expr1(x) || expr2(x));

Func<T, bool> NOTexpr1 = (x => !expr1(x));

answered Nov 13 '15 at 15:11

Céline

1

this cannot be used in Linq to SQL for instance
– Romain Vergnory
May 12 '16 at 9:47

add a comment |

-7

I think this works fine, isn't it ?

Func<T, bool> expr1 = (x => x.Att1 == "a");

Func<T, bool> expr2 = (x => x.Att2 == "b");

Func<T, bool> expr1ANDexpr2 = (x => expr1(x) && expr2(x));

Func<T, bool> expr1ORexpr2 = (x => expr1(x) || expr2(x));

Func<T, bool> NOTexpr1 = (x => !expr1(x));

answered Nov 13 '15 at 15:11

Céline

1

this cannot be used in Linq to SQL for instance
– Romain Vergnory
May 12 '16 at 9:47

add a comment |

-7

I think this works fine, isn't it ?

Func<T, bool> expr1 = (x => x.Att1 == "a");

Func<T, bool> expr2 = (x => x.Att2 == "b");

Func<T, bool> expr1ANDexpr2 = (x => expr1(x) && expr2(x));

Func<T, bool> expr1ORexpr2 = (x => expr1(x) || expr2(x));

Func<T, bool> NOTexpr1 = (x => !expr1(x));

answered Nov 13 '15 at 15:11

Céline

I think this works fine, isn't it ?

Func<T, bool> expr1 = (x => x.Att1 == "a");

Func<T, bool> expr2 = (x => x.Att2 == "b");

Func<T, bool> expr1ANDexpr2 = (x => expr1(x) && expr2(x));

Func<T, bool> expr1ORexpr2 = (x => expr1(x) || expr2(x));

Func<T, bool> NOTexpr1 = (x => !expr1(x));

answered Nov 13 '15 at 15:11

Céline

answered Nov 13 '15 at 15:11

Céline

answered Nov 13 '15 at 15:11

Céline

answered Nov 13 '15 at 15:11

Céline

1

this cannot be used in Linq to SQL for instance
– Romain Vergnory
May 12 '16 at 9:47

add a comment |

1

this cannot be used in Linq to SQL for instance
– Romain Vergnory
May 12 '16 at 9:47

this cannot be used in Linq to SQL for instance
– Romain Vergnory
May 12 '16 at 9:47

add a comment |

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