On May 30, 8:15 pm, kanepa...@hotmail.com wrote:

try isDigit and isChar functions when validating the .keydown action.

kanepa...@hotmail.com wrote:

This is not complete but something like this I gues:

You can add  KeyDown event handler to your textbox ...  for example:

private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
     if(e.KeyCode == Keys.OemMinus) // and of course more checks
here ....
     {
          e.SuppressKeyPress = true;
          e.Handled = true;
      }
 }

//
// AlphaNumTextBox.cs
//

using System;
using System.Windows.Forms;

namespace AlphaNumericTextBox
{
   /// <remarks>
   /// A text box to contain alphanumeric data
   /// </remarks>
   internal sealed class AlphaNumTextBox : TextBox
   {
       #region Fields

       private bool isBack = false;
       private bool isAlphaNum = false;

       #endregion

       #region Event raisers

       protected override void OnKeyDown(KeyEventArgs e)
       {
           Keys k = e.KeyCode;

           if (k == Keys.Back)
           {
               this.isBack =  true;
               this.isAlphaNum = false;
           }
           else
           {
               bool isAlpha = !e.Alt && !e.Control && (k >= Keys.A && k <=
Keys.Z);

               // Determine whether the keystroke is a number
               bool d0d9 = k >= Keys.D0 && k <= Keys.D9;
               bool numpad = k >= Keys.NumPad0 && k <= Keys.NumPad9;
               bool isNumber = (!e.Alt && !e.Control && !e.Shift) && (d0d9

               this.isBack = false;
               this.isAlphaNum = isAlpha || isNumber;
           }
           base.OnKeyDown(e);
       }

       protected override void OnKeyPress(KeyPressEventArgs e)
       {
           if (!this.isBack && !this.isAlphaNum)
           {
               e.Handled = true;
               return;
           }

           char c = e.KeyChar;

           if (this.isBack && this.SelectionStart > 0)
           {
               int currentPosition = SelectionStart;
               this.Text = this.Text.Substring(0, this.TextLength - 1);
               this.SelectionStart = currentPosition - 1;
               e.Handled = true;
               return;
           }

           if (this.isAlphaNum && this.SelectionStart < this.MaxLength)
           {
               int currentPosition = SelectionStart;
               this.Text = this.Text.Insert(currentPosition,
Char.ToUpper(c).ToString());
               this.SelectionStart = currentPosition + 1;
               e.Handled = true;
               return;
           }

           base.OnKeyPress(e);
       }

       #endregion
   }
}

Bye,
Luigi.

Filtering at key-press is usually the bad approach.
It will mess-up a languages that have more complex input
(dead-keys, IME, etc.)