C#

rajeevkuth wrote:

But this can not distinguish between capital letters and small letters. How can I permit only small letters?

rajeevkuth wrote:

The sad part is, TextBox does not expose such an event from which I can get KeyPressEventArgs.

Where do you get such nonsense? In WinForms every Control has the same three keyboard events.

rajeevkuth wrote:

How can I permit only small letters?

Bastard Programmer from Hell

public class SpecialTextboxCasing : Behavior<TextBox>
{
  protected override void OnAttached()
  {
    base.OnAttached();   
    AssociatedObject.PreviewTextInput += AssociatedObject_PreviewTextInput;
    DataObject.AddPastingHandler(AssociatedObject, OnClipboardPaste);
  }

  protected override void OnDetaching()
  {
    base.OnDetaching();
    AssociatedObject.PreviewTextInput -= AssociatedObject_PreviewTextInput;
    DataObject.RemovePastingHandler(AssociatedObject, OnClipboardPaste);
  }

  private void OnClipboardPaste(object sender, DataObjectPastingEventArgs dopea)
  {
    // Do something...
  }

  void AssociatedObject_PreviewTextInput(object sender, TextCompositionEventArgs e)
  {
    // Do something...
  }
}

void textBox1_KeyPress(object sender, KeyPressEventArgs e)
     {
         if (e.KeyChar.ToString() == e.KeyChar.ToString().ToUpper())
         {
             MessageBox.Show("Only Small Letters are Permitted");
             e.Handled = true;
         }

     }

e.KeyChar = e.KeyChar.ToString().ToLower().ToCharArray()[0];