[VB] Newbie Question

[anakinsolois]

Lets say i have this text box in which i need only a numerical input. How do i go about setting a condition which only accepts numeric values?

btw, im using Visual Studio 2005

[azcodemonkey]

Here's how I would do it. Create handlers for the Validating and Validated events. Add an Error Provider control to your form. Inside your Validating handler, do this:

   Private Sub ValidatingHandler(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles TextBox1.Validating
        Dim tb As TextBox
        If TypeOf sender Is TextBox Then
            tb = CType(sender, TextBox)
            Try
                If tb.Text.Length > 0 Then
                    Integer.Parse(tb.Text)
                End If
            Catch
                ErrorProvider1.SetError(tb, "Input should be numeric only")
                e.Cancel = True
            End Try
        End If
    End Sub

Then in my Validated handler, I'd do this:

   Private Sub ValidatedHandler(ByVal sender As Object, ByVal e As EventArgs) Handles TextBox1.Validated
        If TypeOf sender Is TextBox Then
            Dim tb As TextBox = CType(sender, TextBox)
            ErrorProvider1.SetError(tb, "")
        End If
    End Sub

In your constructor, or New subprocedure, you can add other controls to use the handlers for validating.

       'Add any initialization after the InitializeComponent() call
        AddHandler TextBox2.Validating, AddressOf ValidatingHandler
        AddHandler TextBox2.Validated, AddressOf ValidatedHandler

[anakinsolois]

Thanks for the helper weenur, nut im not too good with VB. Heres my code:

Public Class Temperature_Convertor
    Dim choice As Boolean
    Private Sub rbtCentigrade_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles rbtCentigrade.CheckedChanged
        choice = True
    End Sub
    Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles rbtFarenheitToCentigrade.CheckedChanged
        choice = False
    End Sub

    Private Sub btnConvert_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConvert.Click
        Dim n As String
        n = txtInput.Text
        If n <> "" Then
            'Add check for non-numeric value here
            Conversion()
        Else
            MessageBox.Show("Enter a value before clicking", "Error")
        End If
    End Sub
    Sub Conversion()
        Dim n As String
        n = txtInput.Text
        If choice = True Then
            n = (n * 180 / 100) - 32
            MessageBox.Show("Value in Fahrenheit is " & n, "Fahrenheit Answer")
        Else
            n = (n + 32) * 100 / 180
            MessageBox.Show("Value in Centigrade is " & n, "Centigrade Answer")
        End If
    End Sub
End Class

All I want is something that checks of n is a numeric value where it says "'Add check for non-numeric value here". To me this seems a bit complicated just to make a small check like that. If theres no other way, where would i put the code you gave me?

[azcodemonkey]

You could use the IsNumeric function.

'...
       Dim n As String
       n = txtInput.Text
       If n <> "" Then
           'Add check for non-numeric value here
           If Microsoft.VisualBasic.IsNumeric( n ) = True Then
               Conversion()
           Else
                ' Add message
           End If
       Else
'etc...

It may be a good idea to not use text boxes and instead use a NumericUpDown control. It prevents the entry of non-numeric characters right off the bat.

[anakinsolois]

Thanks, im using the NumericUpDown Control, its a bit easier. Just one thing, it it possible to make the scroll arrows on the box disappear?

EDIT : Also, i click the button, it computes the value and resets to 0 or 100. How do i stop it from happening?

Edited July 21, 2004 by anakinsolois

[anthonycara]

why not use a MaskedEditBox control? It should be on your system. Ctrl + T and look for the Microsoft MaskedEdit Control, and set it's input type to numeric ;)

and you could use ### for a certain number of digits if you wanted :)

[anakinsolois]

Thanks, ill try that out now