Mixing
How to group a table by a certain attribute then count those elements that are present in an other table...
-2
Let's say I have two tables (entities):
class Person
{
public int Id { get; set; } // primary key
public string City { get; set; } // the attribute to group by
}
class JoinTable
{
public int Id { get; set; } // primary key
public int Person_Id { get; set; } // foreign key referencing a Person entity/row
public int SomeOther_Id { get; set; } // foreign key referencing some other irrelevant entity/row
}
I want to group all Person entities by their "City" attribute and count how many people are referenced in the JoinTable by each city.
How do I query that in LINQ?
c# linq
edited Jan 2 at 17:40
kara
1,86431124
asked Jan 2 at 15:30
L.Z.L.Z.
11
add a comment |
-2
Let's say I have two tables (entities):
class Person
{
public int Id { get; set; } // primary key
public string City { get; set; } // the attribute to group by
}
class JoinTable
{
public int Id { get; set; } // primary key
public int Person_Id { get; set; } // foreign key referencing a Person entity/row
public int SomeOther_Id { get; set; } // foreign key referencing some other irrelevant entity/row
}
I want to group all Person entities by their "City" attribute and count how many people are referenced in the JoinTable by each city.
How do I query that in LINQ?
c# linq
edited Jan 2 at 17:40
kara
1,86431124
asked Jan 2 at 15:30
L.Z.L.Z.
11
add a comment |
-2
-2
-2
Let's say I have two tables (entities):
class Person
{
public int Id { get; set; } // primary key
public string City { get; set; } // the attribute to group by
}
class JoinTable
{
public int Id { get; set; } // primary key
public int Person_Id { get; set; } // foreign key referencing a Person entity/row
public int SomeOther_Id { get; set; } // foreign key referencing some other irrelevant entity/row
}
I want to group all Person entities by their "City" attribute and count how many people are referenced in the JoinTable by each city.
How do I query that in LINQ?
c# linq
edited Jan 2 at 17:40
kara
1,86431124
asked Jan 2 at 15:30
L.Z.L.Z.
11
Let's say I have two tables (entities):
class Person
{
public int Id { get; set; } // primary key
public string City { get; set; } // the attribute to group by
}
class JoinTable
{
public int Id { get; set; } // primary key
public int Person_Id { get; set; } // foreign key referencing a Person entity/row
public int SomeOther_Id { get; set; } // foreign key referencing some other irrelevant entity/row
}
I want to group all Person entities by their "City" attribute and count how many people are referenced in the JoinTable by each city.
How do I query that in LINQ?
c# linq
c# linq
edited Jan 2 at 17:40
kara
1,86431124
asked Jan 2 at 15:30
L.Z.L.Z.
11
edited Jan 2 at 17:40
kara
1,86431124
asked Jan 2 at 15:30
L.Z.L.Z.
11
edited Jan 2 at 17:40
kara
1,86431124
edited Jan 2 at 17:40
kara
1,86431124
edited Jan 2 at 17:40
kara
1,86431124
1,86431124
asked Jan 2 at 15:30
L.Z.L.Z.
11
asked Jan 2 at 15:30
L.Z.L.Z.
11
asked Jan 2 at 15:30
L.Z.L.Z.
11
11
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
0
I'm not quite sure, what you want to acchieve. But i think something like this:
// Example Data (would be great if you could write some in your questions..)
List<Person> ps = new List<Person>()
{
new Person() { Id = 1, City = "Cologne" },
new Person() { Id = 2, City = "Cologne" },
new Person() { Id = 3, City = "Berlin" },
new Person() { Id = 4, City = "Berlin" },
};
List<JoinTable> join = new List<JoinTable>()
{
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 3000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 4000 },
};
// Join the Table and select a new object.
var tmp = ps.Join(
join, // which table/list should be joined
o => o.Id, // key of outer list
i => i.Person_Id, // key of inner list
(o, i) => new { City = o.City, Id = i.Id, SomeOtherId = i.SomeOther_Id}); // form a new object with three properties..
// now we can group out new objects
var groupingByCity = tmp.GroupBy(g => g.City);
// let's see what we got..
foreach (var g in groupingByCity)
{
Console.WriteLine(g.Key + ": " + g.Count());
foreach (var g2 in g.GroupBy(a => a.SomeOtherId)) // And yes we can group out values again..
{
Console.WriteLine(" " + g2.Key + ": " + g2.Count());
}
}
answered Jan 2 at 16:06
karakara
1,86431124
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
0
I'm not quite sure, what you want to acchieve. But i think something like this:
// Example Data (would be great if you could write some in your questions..)
List<Person> ps = new List<Person>()
{
new Person() { Id = 1, City = "Cologne" },
new Person() { Id = 2, City = "Cologne" },
new Person() { Id = 3, City = "Berlin" },
new Person() { Id = 4, City = "Berlin" },
};
List<JoinTable> join = new List<JoinTable>()
{
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 3000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 4000 },
};
// Join the Table and select a new object.
var tmp = ps.Join(
join, // which table/list should be joined
o => o.Id, // key of outer list
i => i.Person_Id, // key of inner list
(o, i) => new { City = o.City, Id = i.Id, SomeOtherId = i.SomeOther_Id}); // form a new object with three properties..
// now we can group out new objects
var groupingByCity = tmp.GroupBy(g => g.City);
// let's see what we got..
foreach (var g in groupingByCity)
{
Console.WriteLine(g.Key + ": " + g.Count());
foreach (var g2 in g.GroupBy(a => a.SomeOtherId)) // And yes we can group out values again..
{
Console.WriteLine(" " + g2.Key + ": " + g2.Count());
}
}
answered Jan 2 at 16:06
karakara
1,86431124
add a comment |
0
I'm not quite sure, what you want to acchieve. But i think something like this:
// Example Data (would be great if you could write some in your questions..)
List<Person> ps = new List<Person>()
{
new Person() { Id = 1, City = "Cologne" },
new Person() { Id = 2, City = "Cologne" },
new Person() { Id = 3, City = "Berlin" },
new Person() { Id = 4, City = "Berlin" },
};
List<JoinTable> join = new List<JoinTable>()
{
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 3000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 4000 },
};
// Join the Table and select a new object.
var tmp = ps.Join(
join, // which table/list should be joined
o => o.Id, // key of outer list
i => i.Person_Id, // key of inner list
(o, i) => new { City = o.City, Id = i.Id, SomeOtherId = i.SomeOther_Id}); // form a new object with three properties..
// now we can group out new objects
var groupingByCity = tmp.GroupBy(g => g.City);
// let's see what we got..
foreach (var g in groupingByCity)
{
Console.WriteLine(g.Key + ": " + g.Count());
foreach (var g2 in g.GroupBy(a => a.SomeOtherId)) // And yes we can group out values again..
{
Console.WriteLine(" " + g2.Key + ": " + g2.Count());
}
}
answered Jan 2 at 16:06
karakara
1,86431124
add a comment |
0
0
0
I'm not quite sure, what you want to acchieve. But i think something like this:
// Example Data (would be great if you could write some in your questions..)
List<Person> ps = new List<Person>()
{
new Person() { Id = 1, City = "Cologne" },
new Person() { Id = 2, City = "Cologne" },
new Person() { Id = 3, City = "Berlin" },
new Person() { Id = 4, City = "Berlin" },
};
List<JoinTable> join = new List<JoinTable>()
{
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 3000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 4000 },
};
// Join the Table and select a new object.
var tmp = ps.Join(
join, // which table/list should be joined
o => o.Id, // key of outer list
i => i.Person_Id, // key of inner list
(o, i) => new { City = o.City, Id = i.Id, SomeOtherId = i.SomeOther_Id}); // form a new object with three properties..
// now we can group out new objects
var groupingByCity = tmp.GroupBy(g => g.City);
// let's see what we got..
foreach (var g in groupingByCity)
{
Console.WriteLine(g.Key + ": " + g.Count());
foreach (var g2 in g.GroupBy(a => a.SomeOtherId)) // And yes we can group out values again..
{
Console.WriteLine(" " + g2.Key + ": " + g2.Count());
}
}
answered Jan 2 at 16:06
karakara
1,86431124
I'm not quite sure, what you want to acchieve. But i think something like this:
// Example Data (would be great if you could write some in your questions..)
List<Person> ps = new List<Person>()
{
new Person() { Id = 1, City = "Cologne" },
new Person() { Id = 2, City = "Cologne" },
new Person() { Id = 3, City = "Berlin" },
new Person() { Id = 4, City = "Berlin" },
};
List<JoinTable> join = new List<JoinTable>()
{
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 1, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 1000 },
new JoinTable() { Id = 1, Person_Id = 2, SomeOther_Id = 2000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 3000 },
new JoinTable() { Id = 1, Person_Id = 3, SomeOther_Id = 4000 },
};
// Join the Table and select a new object.
var tmp = ps.Join(
join, // which table/list should be joined
o => o.Id, // key of outer list
i => i.Person_Id, // key of inner list
(o, i) => new { City = o.City, Id = i.Id, SomeOtherId = i.SomeOther_Id}); // form a new object with three properties..
// now we can group out new objects
var groupingByCity = tmp.GroupBy(g => g.City);
// let's see what we got..
foreach (var g in groupingByCity)
{
Console.WriteLine(g.Key + ": " + g.Count());
foreach (var g2 in g.GroupBy(a => a.SomeOtherId)) // And yes we can group out values again..
{
Console.WriteLine(" " + g2.Key + ": " + g2.Count());
}
}
answered Jan 2 at 16:06
karakara
1,86431124
answered Jan 2 at 16:06
karakara
1,86431124
answered Jan 2 at 16:06
karakara
1,86431124
answered Jan 2 at 16:06
karakara
1,86431124
1,86431124
add a comment |
add a comment |
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