You can do this with the use of Ascii integers. Put this code in the Textbox’s Keypress event. e.KeyChar
represents the key that’s pressed. And the the built-in function Asc()
converts it into its Ascii integer.
Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
'97 - 122 = Ascii codes for simple letters
'65 - 90 = Ascii codes for capital letters
'48 - 57 = Ascii codes for numbers
If Asc(e.KeyChar) <> 8 Then
If Asc(e.KeyChar) < 48 Or Asc(e.KeyChar) > 57 Then
e.Handled = True
End If
End If
End Sub