C# PreviewKeyDown Event - Allow Special Characters

Hello,

I have a textbox and a PreviewKeyDown Event in which i want to allow Special Characters,A-Z and 0-9 only. Other keys such as keyboard modifiers, F1-F12, Esc,Tab, etc are not allowed.

 private void PART_SearchText_PreviewKeyDown(object sender, KeyEventArgs e)
        {
            TextBox searchTextBox = sender as TextBox;

           if (((e.Key >= Key.A && e.Key <= Key.Z)
                || (e.Key >= Key.D0 && e.Key <= Key.D9)
                || (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9)
                || (e.Key == Key.Back || e.Key == Key.Delete))&& (Keyboard.Modifiers != ModifierKeys.Shift)&& (Keyboard.Modifiers != ModifierKeys.Alt)&& (Keyboard.Modifiers != ModifierKeys.Control)&& (Keyboard.Modifiers != ModifierKeys.Windows)&& (searchTextBox.SelectedText.Length > 0 && searchTextBox.Text.Length > 0)&& (searchTextBox.SelectedText.Length == searchTextBox.Text.Length))
            {
                if (SearchDeletionCommand != null)
                {
                    searchTextBox.IsReadOnly = false;
                    SearchDeletionCommand.Execute(null);
                }
            }
      }

The issue I am facing when hitting special characters (!,@,#...).

So on my laptop if i press Shift 1, i am eventually entering a punctuation mark (!) and that should work. But in above code what happens is that the conditions does not get satisfied.

Thanks,

Abdi