How do I validate a user input and discard the input if it is not numeric?

How do I validate a user input and discard the input if it is not numeric? My code: 
private void txtQuantity_KeyPress(object sender, 
System.Windows.Forms.KeyPressEventArgs e)
		{
			if (char.IsDigit(e.KeyChar)  == false)
			{
				MyErrorProvider.SetError(txtQuantity,"Please
Enter a Numeric Value");
				}
			else
				MyErrorProvider.SetError(txtQuantity,"");
		}

From MSDN Help:
"Set Handled to true to cancel the KeyPress event. This keeps the control from processing the key press."

The "proper" C# code would be: 

private void txtQuantity_KeyPress(object sender, KeyPressEventArgs e)
{
 if (!char.IsDigit(e.KeyChar))
 {
  MyErrorProvider.SetError(txtQuantity,"Please Enter a Numeric 
Value");
  e.Handled = true;
 }
 else
 {
  MyErrorProvider.SetError(txtQuantity,"");
 }
}

This was first published in July 2003

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