preventing users from entering characters in a textbox allowing only numbers

[ethicalhacker]

How can I prevent users from entering characters in a textbox such that only numbers get entered in the textbox?

 

[.paul.]

heres a class that only allows numeric input

Public Class TextBoxEx
    Inherits System.Windows.Forms.TextBox

    Private _allowNegative As Boolean
    Private _enterTabbing As Boolean
    Private _previousText As String = ""

    Public Property allowNegative() As Boolean
        Get
            allowNegative = _allowNegative
        End Get
        Set(ByVal value As Boolean)
            _allowNegative = value
        End Set
    End Property

    Public Property enterTabbing() As Boolean
        Get
            enterTabbing = _enterTabbing
        End Get
        Set(ByVal value As Boolean)
            _enterTabbing = value
        End Set
    End Property

    Private ReadOnly Property previousText() As String
        Get
            previousText = _previousText
        End Get
    End Property

    Protected Overrides Sub OnKeyPress(ByVal e As System.Windows.Forms.KeyPressEventArgs)
        MyBase.OnKeyPress(e)

        If enterTabbing Then
            If Asc(e.KeyChar) = 13 And Me.SelectionStart = Me.Text.Length Or Asc(e.KeyChar) = 13 And Me.SelectionLength = Me.Text.Length Then
                Me.Parent.SelectNextControl(Me, True, True, False, True)
                Exit Sub
            End If
        End If

        If allowNegative Then
            If Not IsNumeric(e.KeyChar) Then
                If Not e.KeyChar = "." And Not e.KeyChar = "-" And Asc(e.KeyChar) <> 8 Or Me.Text.Contains(".") = True And Asc(e.KeyChar) <> 8 Or Not e.KeyChar = "." And Asc(e.KeyChar) <> 8 And Me.SelectionStart > 0 And e.KeyChar = "-" Then
                    e.KeyChar = Nothing
                End If
            End If
        Else
            If Not IsNumeric(e.KeyChar) Then
                If Not e.KeyChar = "." And Asc(e.KeyChar) <> 8 Or Me.Text.Contains(".") = True And Asc(e.KeyChar) <> 8 Then
                    e.KeyChar = Nothing
                End If
            End If
        End If

    End Sub

    Protected Overrides Sub OnTextChanged(ByVal e As System.EventArgs)
        MyBase.OnTextChanged(e)

        If allowNegative Then
            If Me.Text = "." Or Me.Text = "-" Or Me.Text = "-." Or Me.Text = "" Or IsNumeric(Me.Text) Then
                _previousText = Me.Text
            Else
                Me.Text = previousText
            End If
            Me.SelectionStart = Me.Text.Length
        Else
            If Me.Text = "." Or Me.Text = "" Or IsNumeric(Me.Text) Then
                _previousText = Me.Text
            Else
                Me.Text = previousText
            End If
            Me.SelectionStart = Me.Text.Length
        End If
    End Sub

End Class

 

[ethicalhacker]

never mind I got it
heres the code:

For only Numeric Input
If Char.IsNumber(e.KeyChar) = False Then
If e.KeyChar = CChar(ChrW(Keys.Back)) or e.KeyChar = CChar(ChrW(
Keys.Space)) Then
e.Handled = False
Else
e.Handled = True
End If
End If
It works great for me hope it works with everyone!

For only Alphabetical Input

If Char.IsLetter(e.KeyChar) = False Then
If e.KeyChar = CChar(ChrW(Keys.Back)) or e.KeyChar = CChar(ChrW(
Keys.Space)) Then
e.Handled = False
Else
e.Handled = True
End If
End If

For only Alphanumeric Input

If Char.IsLetterOrDigit(e.KeyChar) = False Then
If e.KeyChar = CChar(ChrW(Keys.Back)) or e.KeyChar = CChar(ChrW(
Keys.Space)) Then
e.Handled = False
Else
e.Handled = True
End If
End If

For only Decimal Input

If Char.IsNumber(e.KeyChar) = False Then
If e.KeyChar = CChar(ChrW(Keys.Back)) Or e.KeyChar =
CChar(".") or e.KeyChar = CChar(ChrW(Keys.Space)) Then
e.Handled = False
Else
e.Handled = True
End If
End If

 

[JohnH]

Use a NumericUpDown control or a MaskedTextBox control.

 

[bscvc99]

a simple way to do it is

If IsNumeric(TextBox1.Text) Then
Else
TextBox1.ResetText()
End If

however if you need to allow decimal points then one of the above mentioned solutions is needed.

 

[JuggaloBrotha]

Personally, I use the NumericUpDown control for this instead of a TextBox, the NumericUpDown control allows you to specify a minimum number, maximum number, how many decimal places are allowed, etc...

Then you simply use the .Value() property to grab whatever the user typed in