1 private void textBox3_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e) 2 { 3     //阻止从键盘输入键 4     e.Handled = true; 5     if(e.KeyChar>='0' && e.KeyChar <='9') 6     { 7         e.Handled = false; 8     } 9 10 }11 或者12 private void tbID_KeyPress(object sender, KeyPressEventArgs e)13         {14             if (!((e.KeyChar >= '0' && e.KeyChar <= '9') || e.KeyChar == ' '))//不输入输入除了数字之外的所有非法字符的判断15             {16                 e.Handled = true;17             }18         }19 20 21 多条件的：22 23 private void TxtUser_KeyPress(object sender, KeyPressEventArgs e)24         {25             //阻止从键盘输入键26            e.Handled = true;27 28             if ((e.KeyChar >= '0' && e.KeyChar <= '9') || (e.KeyChar == (char)8))29             {30 31                 if ((e.KeyChar == (char)8)) { e.Handled = false; return; }32                 else33                 {34                     int len = TxtUser.Text.Length;35                     if (len < 5)36                     {37                         if (len == 0 && e.KeyChar != '0')38                         {39                             e.Handled = false; return;40                         }41                         else if(len == 0)42                         {43                             MessageBox.Show("编号不能以0开头！"); return;44                         }45                         e.Handled = false; return;46                     }47                     else48                     {49                         MessageBox.Show("编号最多只能输入5位数字！");50                     }51                 }52             }53             else54             {55                 MessageBox.Show("编号只能输入数字！");56             }57            58 59         }