How to disallow zero in textbox using char.IsDigit

February 3, 2023

I have the below code wherein it works for only numbers and backspace but I want to also have that no zeros are allowed, but it is not working

private void TxtNumber4_KeyPress(object sender, KeyPressEventArgs e)
        {
            if ((char.IsDigit(e.KeyChar)) || (char.IsControl(e.KeyChar)) || (int)e.KeyChar == 0)
            {
                errorProvider1.SetError(LblNum2, "");
                LblNum2.Text = "";
            }
            else
            {
                e.Handled = true;
                errorProvider1.SetError(LblNum2, "Allow Only Numeric Values !");
                LblNum2.Text = "Allow Only Numeric Values !";
            }
        }

>Solution :

Let’s start from the other end, i.e. what we allow: '1'..'9' (note they are chars, say '1' is not int 1) and all the control chars:

private void TxtNumber4_KeyPress(object sender, KeyPressEventArgs e) {
  // If e.KeyChar is a control character
  //   or it some char from '1'..'9' we allow it
  if (char.IsControl(e.KeyChar) || e.KeyChar >= '1' && e.KeyChar <= '9') {
    errorProvider1.SetError(LblNum2, "");
    LblNum2.Text = "";
  }
  else {
    e.Handled = true;
    errorProvider1.SetError(LblNum2, "Allow Only Numeric Values !");
    LblNum2.Text = "Allow Only Numeric Values !";
  }
}