How to make TextBox to receive only number key values using KeyDown Event in C#?

Question

This code in my form updates the textBox1.Text twice whenever number keys are pressed.

private void textBox1_KeyDown( object sender, KeyEventArgs e )          


        

Answer 1

You can try like this:

private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
   e.SuppressKeyPress = !(e.KeyValue >= 48 && e.KeyValue <= 57);
}

Check New keyboard APIs: KeyEventArgs.SuppressKeyPress

The problem is that "Handled" doesn't take care of pending WM_CHAR messages already built up in the message queue - so setting Handled = true does not prevent a KeyPress from occurring.

In order not to break anyone who has currently got e.Handled = true, we needed to add a new property called SuppressKeyChar. If we went the other way, if "handling" a keydown suddenly started to actually work, we might break folks who accidentally had this set to true.