[RESOLVED] [ask] textbox only accept hex

[allopiloping]

i want to make a textbox that only can support the hex number.

how to make the validation???

thx a lot

[Joacim Andersson]

Here is one way of doing it:

  Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
    If Not "1234567890ABCDEF".Contains(Char.ToUpper(e.KeyChar)) AndAlso e.KeyChar <> vbBack Then
      e.Handled = True
    End If
  End Sub

The above will not allow the user to type in anything but hexadecimal characters, however it's not bullet proof since you could still paste something that contains something else so you should always validate the string. Passing it to the following function could do that:

  Public Function IsHex(ByVal str As String) As Boolean
    Try
      Dim num As Long = CLng("&H" & str)
      Return True
    Catch ex As Exception
      Return False
    End Try
  End Function

[alex_read]

There is the following method which you might want to research in a bit more depth which might be of help to you:

Integer.Parse(stringToEvaluate, Globalization.NumberStyles.HexNumber)

[syntaxeater]

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
e.Handled = Not System.Uri.IsHexDigit(e.KeyChar)
End Sub

[allopiloping]

thx

it works

[syntaxeater]

yw

thread resolve

[MaximilianMayrhofer]

Aren't you better off handling the text-changed event to cover copy-pasting?

[syntaxeater]

Hmm, good point. Well then, there's only one sane, logical thing to do...

...And thats to erase the functionality of TextBoxBase's paste!

Dim PasteMethod As Reflection.MethodInfo = _
    Array.Find(Of Reflection.MethodInfo)(DirectCast(TextBox1, TextBoxBase).GetType.GetMethods, _
    New Predicate(Of Reflection.MethodInfo)(Function(meth As Reflection.MethodInfo) meth.Name = "Paste"))
Dim newPaste() As Byte = {0, 0, 0, 0, 0, 0, 0, 42}
Dim hndlePaste As System.Runtime.InteropServices.GCHandle = _
    System.Runtime.InteropServices.GCHandle.Alloc(CType(newPaste, Object), System.Runtime.InteropServices.GCHandleType.Pinned)
Dim addPaste As IntPtr = hndlePaste.AddrOfPinnedObject()
System.Reflection.Emit.MethodRental.SwapMethodBody(GetType(TextBoxBase), PasteMethod.MetadataToken, addPaste, newPaste.Length, _
    System.Reflection.Emit.MethodRental.JitImmediate)

Muahahaha! :evil:

Unfortunately, Microsoft frowns on this and won't let me modify anything that has already been loaded by the JIT.

So since we can't do that - yeah, Text_Change event is probably best.
</joke>