VB.net: “Input string was not in a correct format.” Using Convert.ToDouble

-1

I keep receiving the error mention in the title. I've tried replacing all "+" with "&" as mentioned in other threads, but it doesn't seem to work. I wanted to create a program that allows me to see my weight on other planets using VB.net but I cannot get past this "Input string was not in a correct format" error. Any help please? The error occurs at the first line.

                    Convert.ToDouble(ComboBox1.SelectedItem())

    If ComboBox1.SelectedItem = 0 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.378)

    ElseIf ComboBox1.SelectedItem = 1 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.905)

    ElseIf ComboBox1.SelectedItem = 2 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.0)

    ElseIf ComboBox1.SelectedItem = 3 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.379)

    ElseIf ComboBox1.SelectedItem = 4 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 2.529)

    ElseIf ComboBox1.SelectedItem = 5 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.066)

    ElseIf ComboBox1.SelectedItem = 6 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.903)

    ElseIf ComboBox1.SelectedItem = 7 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.096)

    ElseIf ComboBox1.SelectedItem = 8 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.069)

    End If

vb.net

share|improve this question

asked Nov 20 '18 at 20:39

surrealismsurrealism

1

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Always use TryParse instead. You are assuming SelectedItem is a number. Enable "Option Strict On" at the top of your file.
  
  – LarsTech
  Nov 20 '18 at 20:44
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It seems, from your code, that Combobox1.SelectedItem() is probably holding the name of a planet, so converting "Mars" to a double clearly wouldn't work. Perhaps you should be converting TextBox1.Text to double, which looks like it is supposed to be holding a number?
  
  – soohoonigan
  Nov 20 '18 at 20:49
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Do you mean .SelectedIndex? The .Text property of a TextBox is a string. Don't try to multiply strings by numbers even if it appears to work sometimes. Turning on Option Strict will save you odd runtime errors. A user is not guaranteed to enter what you expect.
  
  – Mary
  Nov 20 '18 at 20:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Also, in your "If" statements, I think the Combobox1.SelectedIndex is the property you are after, which will hold an integer. SelectedItem, when cast to a string, will have the planet's name
  
  – soohoonigan
  Nov 20 '18 at 20:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Looks like you intended to check the value ofSelectedIndex, not the SelectedItem?
  
  – Ahmed Abdelhameed
  Nov 20 '18 at 20:51
  
  
  

  
  
  
  

 | 
show 1 more comment

-1

I keep receiving the error mention in the title. I've tried replacing all "+" with "&" as mentioned in other threads, but it doesn't seem to work. I wanted to create a program that allows me to see my weight on other planets using VB.net but I cannot get past this "Input string was not in a correct format" error. Any help please? The error occurs at the first line.

                    Convert.ToDouble(ComboBox1.SelectedItem())

    If ComboBox1.SelectedItem = 0 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.378)

    ElseIf ComboBox1.SelectedItem = 1 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.905)

    ElseIf ComboBox1.SelectedItem = 2 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.0)

    ElseIf ComboBox1.SelectedItem = 3 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.379)

    ElseIf ComboBox1.SelectedItem = 4 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 2.529)

    ElseIf ComboBox1.SelectedItem = 5 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.066)

    ElseIf ComboBox1.SelectedItem = 6 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.903)

    ElseIf ComboBox1.SelectedItem = 7 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.096)

    ElseIf ComboBox1.SelectedItem = 8 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.069)

    End If

vb.net

share|improve this question

asked Nov 20 '18 at 20:39

surrealismsurrealism

1

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Always use TryParse instead. You are assuming SelectedItem is a number. Enable "Option Strict On" at the top of your file.
  
  – LarsTech
  Nov 20 '18 at 20:44
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It seems, from your code, that Combobox1.SelectedItem() is probably holding the name of a planet, so converting "Mars" to a double clearly wouldn't work. Perhaps you should be converting TextBox1.Text to double, which looks like it is supposed to be holding a number?
  
  – soohoonigan
  Nov 20 '18 at 20:49
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Do you mean .SelectedIndex? The .Text property of a TextBox is a string. Don't try to multiply strings by numbers even if it appears to work sometimes. Turning on Option Strict will save you odd runtime errors. A user is not guaranteed to enter what you expect.
  
  – Mary
  Nov 20 '18 at 20:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Also, in your "If" statements, I think the Combobox1.SelectedIndex is the property you are after, which will hold an integer. SelectedItem, when cast to a string, will have the planet's name
  
  – soohoonigan
  Nov 20 '18 at 20:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Looks like you intended to check the value ofSelectedIndex, not the SelectedItem?
  
  – Ahmed Abdelhameed
  Nov 20 '18 at 20:51
  
  
  

  
  
  
  

 | 
show 1 more comment

-1

-1

-1

I keep receiving the error mention in the title. I've tried replacing all "+" with "&" as mentioned in other threads, but it doesn't seem to work. I wanted to create a program that allows me to see my weight on other planets using VB.net but I cannot get past this "Input string was not in a correct format" error. Any help please? The error occurs at the first line.

                    Convert.ToDouble(ComboBox1.SelectedItem())

    If ComboBox1.SelectedItem = 0 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.378)

    ElseIf ComboBox1.SelectedItem = 1 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.905)

    ElseIf ComboBox1.SelectedItem = 2 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.0)

    ElseIf ComboBox1.SelectedItem = 3 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.379)

    ElseIf ComboBox1.SelectedItem = 4 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 2.529)

    ElseIf ComboBox1.SelectedItem = 5 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.066)

    ElseIf ComboBox1.SelectedItem = 6 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.903)

    ElseIf ComboBox1.SelectedItem = 7 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.096)

    ElseIf ComboBox1.SelectedItem = 8 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.069)

    End If

vb.net

share|improve this question

asked Nov 20 '18 at 20:39

surrealismsurrealism

1

I keep receiving the error mention in the title. I've tried replacing all "+" with "&" as mentioned in other threads, but it doesn't seem to work. I wanted to create a program that allows me to see my weight on other planets using VB.net but I cannot get past this "Input string was not in a correct format" error. Any help please? The error occurs at the first line.

                    Convert.ToDouble(ComboBox1.SelectedItem())

    If ComboBox1.SelectedItem = 0 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.378)

    ElseIf ComboBox1.SelectedItem = 1 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.905)

    ElseIf ComboBox1.SelectedItem = 2 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.0)

    ElseIf ComboBox1.SelectedItem = 3 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.379)

    ElseIf ComboBox1.SelectedItem = 4 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 2.529)

    ElseIf ComboBox1.SelectedItem = 5 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.066)

    ElseIf ComboBox1.SelectedItem = 6 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.903)

    ElseIf ComboBox1.SelectedItem = 7 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 1.096)

    ElseIf ComboBox1.SelectedItem = 8 Then

        Label4.Text = "Your weight on " + ComboBox1.SelectedItem() + " is " + (TextBox1.Text * 0.069)

    End If

vb.net

vb.net

share|improve this question

asked Nov 20 '18 at 20:39

surrealismsurrealism

1

share|improve this question

asked Nov 20 '18 at 20:39

surrealismsurrealism

1

share|improve this question

share|improve this question

asked Nov 20 '18 at 20:39

surrealismsurrealism

1

asked Nov 20 '18 at 20:39

surrealismsurrealism

1

asked Nov 20 '18 at 20:39

surrealismsurrealism

1

1

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Always use TryParse instead. You are assuming SelectedItem is a number. Enable "Option Strict On" at the top of your file.
  
  – LarsTech
  Nov 20 '18 at 20:44
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It seems, from your code, that Combobox1.SelectedItem() is probably holding the name of a planet, so converting "Mars" to a double clearly wouldn't work. Perhaps you should be converting TextBox1.Text to double, which looks like it is supposed to be holding a number?
  
  – soohoonigan
  Nov 20 '18 at 20:49
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Do you mean .SelectedIndex? The .Text property of a TextBox is a string. Don't try to multiply strings by numbers even if it appears to work sometimes. Turning on Option Strict will save you odd runtime errors. A user is not guaranteed to enter what you expect.
  
  – Mary
  Nov 20 '18 at 20:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Also, in your "If" statements, I think the Combobox1.SelectedIndex is the property you are after, which will hold an integer. SelectedItem, when cast to a string, will have the planet's name
  
  – soohoonigan
  Nov 20 '18 at 20:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Looks like you intended to check the value ofSelectedIndex, not the SelectedItem?
  
  – Ahmed Abdelhameed
  Nov 20 '18 at 20:51
  
  
  

  
  
  
  

 | 
show 1 more comment

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Always use TryParse instead. You are assuming SelectedItem is a number. Enable "Option Strict On" at the top of your file.
  
  – LarsTech
  Nov 20 '18 at 20:44
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It seems, from your code, that Combobox1.SelectedItem() is probably holding the name of a planet, so converting "Mars" to a double clearly wouldn't work. Perhaps you should be converting TextBox1.Text to double, which looks like it is supposed to be holding a number?
  
  – soohoonigan
  Nov 20 '18 at 20:49
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Do you mean .SelectedIndex? The .Text property of a TextBox is a string. Don't try to multiply strings by numbers even if it appears to work sometimes. Turning on Option Strict will save you odd runtime errors. A user is not guaranteed to enter what you expect.
  
  – Mary
  Nov 20 '18 at 20:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Also, in your "If" statements, I think the Combobox1.SelectedIndex is the property you are after, which will hold an integer. SelectedItem, when cast to a string, will have the planet's name
  
  – soohoonigan
  Nov 20 '18 at 20:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Looks like you intended to check the value ofSelectedIndex, not the SelectedItem?
  
  – Ahmed Abdelhameed
  Nov 20 '18 at 20:51
  
  
  

  
  
  
  

2

2

Always use TryParse instead. You are assuming SelectedItem is a number. Enable "Option Strict On" at the top of your file.

– LarsTech
Nov 20 '18 at 20:44

Always use TryParse instead. You are assuming SelectedItem is a number. Enable "Option Strict On" at the top of your file.

– LarsTech
Nov 20 '18 at 20:44

It seems, from your code, that Combobox1.SelectedItem() is probably holding the name of a planet, so converting "Mars" to a double clearly wouldn't work. Perhaps you should be converting TextBox1.Text to double, which looks like it is supposed to be holding a number?

– soohoonigan
Nov 20 '18 at 20:49

It seems, from your code, that Combobox1.SelectedItem() is probably holding the name of a planet, so converting "Mars" to a double clearly wouldn't work. Perhaps you should be converting TextBox1.Text to double, which looks like it is supposed to be holding a number?

– soohoonigan
Nov 20 '18 at 20:49

Do you mean .SelectedIndex? The .Text property of a TextBox is a string. Don't try to multiply strings by numbers even if it appears to work sometimes. Turning on Option Strict will save you odd runtime errors. A user is not guaranteed to enter what you expect.

– Mary
Nov 20 '18 at 20:51

Do you mean .SelectedIndex? The .Text property of a TextBox is a string. Don't try to multiply strings by numbers even if it appears to work sometimes. Turning on Option Strict will save you odd runtime errors. A user is not guaranteed to enter what you expect.

– Mary
Nov 20 '18 at 20:51

Also, in your "If" statements, I think the Combobox1.SelectedIndex is the property you are after, which will hold an integer. SelectedItem, when cast to a string, will have the planet's name

– soohoonigan
Nov 20 '18 at 20:51

Also, in your "If" statements, I think the Combobox1.SelectedIndex is the property you are after, which will hold an integer. SelectedItem, when cast to a string, will have the planet's name

– soohoonigan
Nov 20 '18 at 20:51

Looks like you intended to check the value ofSelectedIndex, not the SelectedItem?

– Ahmed Abdelhameed
Nov 20 '18 at 20:51

Looks like you intended to check the value ofSelectedIndex, not the SelectedItem?

– Ahmed Abdelhameed
Nov 20 '18 at 20:51

 | 
show 1 more comment

2 Answers
2

active

oldest

votes

0

Thank you all for your help! I solved the problem, by adding CDbl() just before the user input, used Option Strict On, and used SelectedIndex() instead of SelectedItem().

Here is the code:

If ComboBox1.SelectedIndex = 0 Then

        Label4.Text = "Your weight on Mercury" & " is " & (CDbl(TextBox1.Text) * 0.378)

    ElseIf ComboBox1.SelectedIndex = 1 Then

        Label4.Text = "Your weight on Venus" & " is " & (CDbl(TextBox1.Text) * 0.905)

    ElseIf ComboBox1.SelectedIndex = 2 Then

        Label4.Text = "Your weight on Earth" & " is " & (CDbl(TextBox1.Text) * 1.0)

    ElseIf ComboBox1.SelectedIndex = 3 Then

        Label4.Text = "Your weight on Mars" & " is " & (CDbl(TextBox1.Text) * 0.379)

    ElseIf ComboBox1.SelectedIndex = 4 Then

        Label4.Text = "Your weight on Jupiter" & " is " & (CDbl(TextBox1.Text) * 2.529)

    ElseIf ComboBox1.SelectedIndex = 5 Then

        Label4.Text = "Your weight on Saturn" & " is " & (CDbl(TextBox1.Text) * 1.066)

    ElseIf ComboBox1.SelectedIndex = 6 Then

        Label4.Text = "Your weight on Uranus" & " is " & (CDbl(TextBox1.Text) * 0.903)

    ElseIf ComboBox1.SelectedIndex = 7 Then

        Label4.Text = "Your weight on Neptune" & " is " & (CDbl(TextBox1.Text) * 1.096)

    ElseIf ComboBox1.SelectedIndex = 8 Then

        Label4.Text = "Your weight on Pluto" & " is " & (CDbl(TextBox1.Text) * 0.069)

    End If

share|improve this answer

answered Nov 20 '18 at 21:13

surrealismsurrealism

1

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Using CDbl will fail if the user input is not a number. You need to validate the user input to make sure it's a number that can be casted to Double. The standard way of doing so is by using TryParse (Double.TryParse in your case) as suggested by LarsTech in the comments above.
  
  – Ahmed Abdelhameed
  Nov 20 '18 at 22:03
  

  
  
  
  

add a comment | 

0

Use data-binding instead of If else

and Double.TryParse instead of CDbl for conversions from string to integers

and & instead of + when combining strings(or String interpolation).

Option Strict On - always (which you already did)

Public Class Planet

    Public ReadOnly Property Name As String

    Public ReadOnly Property WeightFactor As Double 



    Public Sub New(name As String, weightFactor As Double)

        Me.Name = name 

        Me.WeightFactor = weightFactor

    End Sub     

End Class



' Create planets and bind it to the ComboBox

' Form constructor

Public Sub New()

    InitializeComponent()



    Dim planets As New List(Of Planet) From

    {

        New Planet("Mercury", 0.378),

        New Planet("Venus", 0.905),

        New Planet("Earth", 1.0),

        New Planet("Mars", 0.379),

    }



    ' Bind planets to combobox

    ComboBox1.DisplayMember = "Name" ' Name of the property used for displaying text

    ComboBox1.ValueMember = "WeightFactor" ' Name of the property used as selected value

    ComboBox1.DataSource = planets

End Sub

Then your calculation code will look simpler

Dim personWeight AS Double

If Double.TryParse(textbox1.Text, personWeight) Then

    ' SelectedItem is instance of selected planet

    Dim planet = DirectCast(ComboBox1.SelectedItem, Planet)



    Dim weightOnPlanet = personWeight * planet.WeightFactor

    Label4.Text = $"Your weight on {planet.Name} is {weightOnPlanet}"

End If

share|improve this answer

answered Nov 21 '18 at 2:14

FabioFabio

19.5k22044

add a comment | 

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

active

oldest

votes

active

oldest

votes

0

Thank you all for your help! I solved the problem, by adding CDbl() just before the user input, used Option Strict On, and used SelectedIndex() instead of SelectedItem().

Here is the code:

If ComboBox1.SelectedIndex = 0 Then

        Label4.Text = "Your weight on Mercury" & " is " & (CDbl(TextBox1.Text) * 0.378)

    ElseIf ComboBox1.SelectedIndex = 1 Then

        Label4.Text = "Your weight on Venus" & " is " & (CDbl(TextBox1.Text) * 0.905)

    ElseIf ComboBox1.SelectedIndex = 2 Then

        Label4.Text = "Your weight on Earth" & " is " & (CDbl(TextBox1.Text) * 1.0)

    ElseIf ComboBox1.SelectedIndex = 3 Then

        Label4.Text = "Your weight on Mars" & " is " & (CDbl(TextBox1.Text) * 0.379)

    ElseIf ComboBox1.SelectedIndex = 4 Then

        Label4.Text = "Your weight on Jupiter" & " is " & (CDbl(TextBox1.Text) * 2.529)

    ElseIf ComboBox1.SelectedIndex = 5 Then

        Label4.Text = "Your weight on Saturn" & " is " & (CDbl(TextBox1.Text) * 1.066)

    ElseIf ComboBox1.SelectedIndex = 6 Then

        Label4.Text = "Your weight on Uranus" & " is " & (CDbl(TextBox1.Text) * 0.903)

    ElseIf ComboBox1.SelectedIndex = 7 Then

        Label4.Text = "Your weight on Neptune" & " is " & (CDbl(TextBox1.Text) * 1.096)

    ElseIf ComboBox1.SelectedIndex = 8 Then

        Label4.Text = "Your weight on Pluto" & " is " & (CDbl(TextBox1.Text) * 0.069)

    End If

share|improve this answer

answered Nov 20 '18 at 21:13

surrealismsurrealism

1

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Using CDbl will fail if the user input is not a number. You need to validate the user input to make sure it's a number that can be casted to Double. The standard way of doing so is by using TryParse (Double.TryParse in your case) as suggested by LarsTech in the comments above.
  
  – Ahmed Abdelhameed
  Nov 20 '18 at 22:03
  

  
  
  
  

add a comment | 

0

Thank you all for your help! I solved the problem, by adding CDbl() just before the user input, used Option Strict On, and used SelectedIndex() instead of SelectedItem().

Here is the code:

If ComboBox1.SelectedIndex = 0 Then

        Label4.Text = "Your weight on Mercury" & " is " & (CDbl(TextBox1.Text) * 0.378)

    ElseIf ComboBox1.SelectedIndex = 1 Then

        Label4.Text = "Your weight on Venus" & " is " & (CDbl(TextBox1.Text) * 0.905)

    ElseIf ComboBox1.SelectedIndex = 2 Then

        Label4.Text = "Your weight on Earth" & " is " & (CDbl(TextBox1.Text) * 1.0)

    ElseIf ComboBox1.SelectedIndex = 3 Then

        Label4.Text = "Your weight on Mars" & " is " & (CDbl(TextBox1.Text) * 0.379)

    ElseIf ComboBox1.SelectedIndex = 4 Then

        Label4.Text = "Your weight on Jupiter" & " is " & (CDbl(TextBox1.Text) * 2.529)

    ElseIf ComboBox1.SelectedIndex = 5 Then

        Label4.Text = "Your weight on Saturn" & " is " & (CDbl(TextBox1.Text) * 1.066)

    ElseIf ComboBox1.SelectedIndex = 6 Then

        Label4.Text = "Your weight on Uranus" & " is " & (CDbl(TextBox1.Text) * 0.903)

    ElseIf ComboBox1.SelectedIndex = 7 Then

        Label4.Text = "Your weight on Neptune" & " is " & (CDbl(TextBox1.Text) * 1.096)

    ElseIf ComboBox1.SelectedIndex = 8 Then

        Label4.Text = "Your weight on Pluto" & " is " & (CDbl(TextBox1.Text) * 0.069)

    End If

share|improve this answer

answered Nov 20 '18 at 21:13

surrealismsurrealism

1

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Using CDbl will fail if the user input is not a number. You need to validate the user input to make sure it's a number that can be casted to Double. The standard way of doing so is by using TryParse (Double.TryParse in your case) as suggested by LarsTech in the comments above.
  
  – Ahmed Abdelhameed
  Nov 20 '18 at 22:03
  

  
  
  
  

add a comment | 

0

0

0

Thank you all for your help! I solved the problem, by adding CDbl() just before the user input, used Option Strict On, and used SelectedIndex() instead of SelectedItem().

Here is the code:

If ComboBox1.SelectedIndex = 0 Then

        Label4.Text = "Your weight on Mercury" & " is " & (CDbl(TextBox1.Text) * 0.378)

    ElseIf ComboBox1.SelectedIndex = 1 Then

        Label4.Text = "Your weight on Venus" & " is " & (CDbl(TextBox1.Text) * 0.905)

    ElseIf ComboBox1.SelectedIndex = 2 Then

        Label4.Text = "Your weight on Earth" & " is " & (CDbl(TextBox1.Text) * 1.0)

    ElseIf ComboBox1.SelectedIndex = 3 Then

        Label4.Text = "Your weight on Mars" & " is " & (CDbl(TextBox1.Text) * 0.379)

    ElseIf ComboBox1.SelectedIndex = 4 Then

        Label4.Text = "Your weight on Jupiter" & " is " & (CDbl(TextBox1.Text) * 2.529)

    ElseIf ComboBox1.SelectedIndex = 5 Then

        Label4.Text = "Your weight on Saturn" & " is " & (CDbl(TextBox1.Text) * 1.066)

    ElseIf ComboBox1.SelectedIndex = 6 Then

        Label4.Text = "Your weight on Uranus" & " is " & (CDbl(TextBox1.Text) * 0.903)

    ElseIf ComboBox1.SelectedIndex = 7 Then

        Label4.Text = "Your weight on Neptune" & " is " & (CDbl(TextBox1.Text) * 1.096)

    ElseIf ComboBox1.SelectedIndex = 8 Then

        Label4.Text = "Your weight on Pluto" & " is " & (CDbl(TextBox1.Text) * 0.069)

    End If

share|improve this answer

answered Nov 20 '18 at 21:13

surrealismsurrealism

1

Thank you all for your help! I solved the problem, by adding CDbl() just before the user input, used Option Strict On, and used SelectedIndex() instead of SelectedItem().

Here is the code:

If ComboBox1.SelectedIndex = 0 Then

        Label4.Text = "Your weight on Mercury" & " is " & (CDbl(TextBox1.Text) * 0.378)

    ElseIf ComboBox1.SelectedIndex = 1 Then

        Label4.Text = "Your weight on Venus" & " is " & (CDbl(TextBox1.Text) * 0.905)

    ElseIf ComboBox1.SelectedIndex = 2 Then

        Label4.Text = "Your weight on Earth" & " is " & (CDbl(TextBox1.Text) * 1.0)

    ElseIf ComboBox1.SelectedIndex = 3 Then

        Label4.Text = "Your weight on Mars" & " is " & (CDbl(TextBox1.Text) * 0.379)

    ElseIf ComboBox1.SelectedIndex = 4 Then

        Label4.Text = "Your weight on Jupiter" & " is " & (CDbl(TextBox1.Text) * 2.529)

    ElseIf ComboBox1.SelectedIndex = 5 Then

        Label4.Text = "Your weight on Saturn" & " is " & (CDbl(TextBox1.Text) * 1.066)

    ElseIf ComboBox1.SelectedIndex = 6 Then

        Label4.Text = "Your weight on Uranus" & " is " & (CDbl(TextBox1.Text) * 0.903)

    ElseIf ComboBox1.SelectedIndex = 7 Then

        Label4.Text = "Your weight on Neptune" & " is " & (CDbl(TextBox1.Text) * 1.096)

    ElseIf ComboBox1.SelectedIndex = 8 Then

        Label4.Text = "Your weight on Pluto" & " is " & (CDbl(TextBox1.Text) * 0.069)

    End If

share|improve this answer

answered Nov 20 '18 at 21:13

surrealismsurrealism

1

share|improve this answer

share|improve this answer

answered Nov 20 '18 at 21:13

surrealismsurrealism

1

answered Nov 20 '18 at 21:13

surrealismsurrealism

1

answered Nov 20 '18 at 21:13

surrealismsurrealism

1

1

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Using CDbl will fail if the user input is not a number. You need to validate the user input to make sure it's a number that can be casted to Double. The standard way of doing so is by using TryParse (Double.TryParse in your case) as suggested by LarsTech in the comments above.
  
  – Ahmed Abdelhameed
  Nov 20 '18 at 22:03
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Using CDbl will fail if the user input is not a number. You need to validate the user input to make sure it's a number that can be casted to Double. The standard way of doing so is by using TryParse (Double.TryParse in your case) as suggested by LarsTech in the comments above.
  
  – Ahmed Abdelhameed
  Nov 20 '18 at 22:03
  

  
  
  
  

1

1

Using CDbl will fail if the user input is not a number. You need to validate the user input to make sure it's a number that can be casted to Double. The standard way of doing so is by using TryParse (Double.TryParse in your case) as suggested by LarsTech in the comments above.

– Ahmed Abdelhameed
Nov 20 '18 at 22:03

Using CDbl will fail if the user input is not a number. You need to validate the user input to make sure it's a number that can be casted to Double. The standard way of doing so is by using TryParse (Double.TryParse in your case) as suggested by LarsTech in the comments above.

– Ahmed Abdelhameed
Nov 20 '18 at 22:03

add a comment | 

0

Use data-binding instead of If else

and Double.TryParse instead of CDbl for conversions from string to integers

and & instead of + when combining strings(or String interpolation).

Option Strict On - always (which you already did)

Public Class Planet

    Public ReadOnly Property Name As String

    Public ReadOnly Property WeightFactor As Double 



    Public Sub New(name As String, weightFactor As Double)

        Me.Name = name 

        Me.WeightFactor = weightFactor

    End Sub     

End Class



' Create planets and bind it to the ComboBox

' Form constructor

Public Sub New()

    InitializeComponent()



    Dim planets As New List(Of Planet) From

    {

        New Planet("Mercury", 0.378),

        New Planet("Venus", 0.905),

        New Planet("Earth", 1.0),

        New Planet("Mars", 0.379),

    }



    ' Bind planets to combobox

    ComboBox1.DisplayMember = "Name" ' Name of the property used for displaying text

    ComboBox1.ValueMember = "WeightFactor" ' Name of the property used as selected value

    ComboBox1.DataSource = planets

End Sub

Then your calculation code will look simpler

Dim personWeight AS Double

If Double.TryParse(textbox1.Text, personWeight) Then

    ' SelectedItem is instance of selected planet

    Dim planet = DirectCast(ComboBox1.SelectedItem, Planet)



    Dim weightOnPlanet = personWeight * planet.WeightFactor

    Label4.Text = $"Your weight on {planet.Name} is {weightOnPlanet}"

End If

share|improve this answer

answered Nov 21 '18 at 2:14

FabioFabio

19.5k22044

add a comment | 

0

Use data-binding instead of If else

and Double.TryParse instead of CDbl for conversions from string to integers

and & instead of + when combining strings(or String interpolation).

Option Strict On - always (which you already did)

Public Class Planet

    Public ReadOnly Property Name As String

    Public ReadOnly Property WeightFactor As Double 



    Public Sub New(name As String, weightFactor As Double)

        Me.Name = name 

        Me.WeightFactor = weightFactor

    End Sub     

End Class



' Create planets and bind it to the ComboBox

' Form constructor

Public Sub New()

    InitializeComponent()



    Dim planets As New List(Of Planet) From

    {

        New Planet("Mercury", 0.378),

        New Planet("Venus", 0.905),

        New Planet("Earth", 1.0),

        New Planet("Mars", 0.379),

    }



    ' Bind planets to combobox

    ComboBox1.DisplayMember = "Name" ' Name of the property used for displaying text

    ComboBox1.ValueMember = "WeightFactor" ' Name of the property used as selected value

    ComboBox1.DataSource = planets

End Sub

Then your calculation code will look simpler

Dim personWeight AS Double

If Double.TryParse(textbox1.Text, personWeight) Then

    ' SelectedItem is instance of selected planet

    Dim planet = DirectCast(ComboBox1.SelectedItem, Planet)



    Dim weightOnPlanet = personWeight * planet.WeightFactor

    Label4.Text = $"Your weight on {planet.Name} is {weightOnPlanet}"

End If

share|improve this answer

answered Nov 21 '18 at 2:14

FabioFabio

19.5k22044

add a comment | 

0

0

0

Use data-binding instead of If else

and Double.TryParse instead of CDbl for conversions from string to integers

and & instead of + when combining strings(or String interpolation).

Option Strict On - always (which you already did)

Public Class Planet

    Public ReadOnly Property Name As String

    Public ReadOnly Property WeightFactor As Double 



    Public Sub New(name As String, weightFactor As Double)

        Me.Name = name 

        Me.WeightFactor = weightFactor

    End Sub     

End Class



' Create planets and bind it to the ComboBox

' Form constructor

Public Sub New()

    InitializeComponent()



    Dim planets As New List(Of Planet) From

    {

        New Planet("Mercury", 0.378),

        New Planet("Venus", 0.905),

        New Planet("Earth", 1.0),

        New Planet("Mars", 0.379),

    }



    ' Bind planets to combobox

    ComboBox1.DisplayMember = "Name" ' Name of the property used for displaying text

    ComboBox1.ValueMember = "WeightFactor" ' Name of the property used as selected value

    ComboBox1.DataSource = planets

End Sub

Then your calculation code will look simpler

Dim personWeight AS Double

If Double.TryParse(textbox1.Text, personWeight) Then

    ' SelectedItem is instance of selected planet

    Dim planet = DirectCast(ComboBox1.SelectedItem, Planet)



    Dim weightOnPlanet = personWeight * planet.WeightFactor

    Label4.Text = $"Your weight on {planet.Name} is {weightOnPlanet}"

End If

share|improve this answer

answered Nov 21 '18 at 2:14

FabioFabio

19.5k22044

Use data-binding instead of If else

and Double.TryParse instead of CDbl for conversions from string to integers

and & instead of + when combining strings(or String interpolation).

Option Strict On - always (which you already did)

Public Class Planet

    Public ReadOnly Property Name As String

    Public ReadOnly Property WeightFactor As Double 



    Public Sub New(name As String, weightFactor As Double)

        Me.Name = name 

        Me.WeightFactor = weightFactor

    End Sub     

End Class



' Create planets and bind it to the ComboBox

' Form constructor

Public Sub New()

    InitializeComponent()



    Dim planets As New List(Of Planet) From

    {

        New Planet("Mercury", 0.378),

        New Planet("Venus", 0.905),

        New Planet("Earth", 1.0),

        New Planet("Mars", 0.379),

    }



    ' Bind planets to combobox

    ComboBox1.DisplayMember = "Name" ' Name of the property used for displaying text

    ComboBox1.ValueMember = "WeightFactor" ' Name of the property used as selected value

    ComboBox1.DataSource = planets

End Sub

Then your calculation code will look simpler

Dim personWeight AS Double

If Double.TryParse(textbox1.Text, personWeight) Then

    ' SelectedItem is instance of selected planet

    Dim planet = DirectCast(ComboBox1.SelectedItem, Planet)



    Dim weightOnPlanet = personWeight * planet.WeightFactor

    Label4.Text = $"Your weight on {planet.Name} is {weightOnPlanet}"

End If

share|improve this answer

answered Nov 21 '18 at 2:14

FabioFabio

19.5k22044

share|improve this answer

share|improve this answer

answered Nov 21 '18 at 2:14

FabioFabio

19.5k22044

answered Nov 21 '18 at 2:14

FabioFabio

19.5k22044

answered Nov 21 '18 at 2:14

FabioFabio

19.5k22044

19.5k22044

add a comment | 

add a comment | 

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