.net(c#) winform文本框只能输入数字,不能其他非法字符

 private void textBox3_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
 {
     //阻止从键盘输入键
     e.Handled = true;
     if(e.KeyChar>='' && e.KeyChar <='')
     {
         e.Handled = false;
     }

 }
 或者
 private void tbID_KeyPress(object sender, KeyPressEventArgs e)
         {
             if (!((e.KeyChar >= '' && e.KeyChar <= '') || e.KeyChar == ' '))//不输入输入除了数字之外的所有非法字符的判断
             {
                 e.Handled = true;
             }
         }

 多条件的：

 private void TxtUser_KeyPress(object sender, KeyPressEventArgs e)
         {
             //阻止从键盘输入键
            e.Handled = true;

             if ((e.KeyChar >= '' && e.KeyChar <= '') || (e.KeyChar == (char)))
             {

                 if ((e.KeyChar == (char))) { e.Handled = false; return; }
                 else
                 {
                     int len = TxtUser.Text.Length;
                     if (len < )
                     {
                         if (len ==  && e.KeyChar != '')
                         {
                             e.Handled = false; return;
                         }
                         else if(len == )
                         {
                             MessageBox.Show("编号不能以0开头！"); return;
                         }
                         e.Handled = false; return;
                     }
                     else
                     {
                         MessageBox.Show("编号最多只能输入5位数字！");
                     }
                 }
             }
             else
             {
                 MessageBox.Show("编号只能输入数字！");
             }

         }