Help Making a Calculator in VB

[walpoles93]

As you can probably guess, I'm new to programming and I am teaching myself VB for my Computing course next year. I'm currently working on a calculator project and everthing is fine until the decimal.

Basically I need to ask, if the textbox contains a decimal then don't display another one. My problem is the 'contains' bit. How would I ask if it contains a certain character because at the moment I only know to ask if it is equal.

Sorry if this is a bit vague and thanks in advance.

[jivemasta]

I just went through the same thing for my windows mobile calculator here's my code(in C#, but you should be able to figure out the jist).

if(temp.IndexOf('.')==-1)
temp += ".";

temp is my string version of the number that shows up on the screen. Make sure you aren't casting your string to a double after every button press though, because it will take your decimal off since it thinks 4. is redundant.

[jak]

In VB6 it's

If InStr(Whatever, ".") = 0 Then
    ' Whatever has no dot
End If

[Zayfox]

For VB.NET?

If TextBox.Text.Contains("Text") Then
     Do Something?
Else
     Do moar?
End If

[walpoles93]

Thanks a lot Zayfox, that's exactly what I needed. I ended up with this code:

  Private Sub BtnDec_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnDec.Click
        If Display.Text.Contains(".") Then
            Display.Text = Display.Text
        Else
            Display.Text = Display.Text & "."
        End If
    End Sub

Thanks!

[editline]12:32PM[/editline]

Ok I have antoher question, not related to the project but to the 'contains' thing. How would you ask if it doesn't contain something? I can't find a way to do negatives anywhere.

[jivemasta]

I think in vb you'd use If Not Display.Text.Contains(".") Then...

[OutOfPop]

[QUOTE=walpoles93;16094481]Thanks a lot Zayfox, that's exactly what I needed. I ended up with this code:

  Private Sub BtnDec_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnDec.Click
        If Display.Text.Contains(".") Then
            Display.Text = Display.Text
        Else
            Display.Text = Display.Text & "."
        End If
    End Sub

Thanks!

[editline]12:32PM[/editline]

Ok I have antoher question, not related to the project but to the 'contains' thing. How would you ask if it doesn't contain something? I can't find a way to do negatives anywhere.[/QUOTE]

In If statements, if you want to check for a false response, you stick "Not" infront of it.
So it would be this:

  Private Sub BtnDec_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnDec.Click
        If Not Display.Text.Contains(".") Then     'There were no decimals
            Display.Text = Display.Text
        Else     'There was a decimal
            Display.Text = Display.Text & "."
        End If
    End Sub

[Zayfox]

It's not using the "Not" function.
It's actually this:

If TextBox.Text.Contains("Text") = False Then
     What to do when it doesn't contain "Text"
Else
     What to do when it does contain "Text"
End If

Tested and working.