[Ghoghnus]

کد:

    int t=0;  
        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            string s = e.KeyChar.ToString();
            

            if (!(e.KeyChar >= '0' && e.KeyChar <= '9' || e.KeyChar == '.' && t<1))
            {
               
                e.Handled = true;

            }

if (e.KeyChar == '.') t++;

        }