c#中设置像数量，价格，金额等的textbox的限制条件，用户只能输入数字或小数

        #region 设置数量等textbox控件样式及限制条件（具体调用的方法就是重写或直接调用ShieldNumberTextBoxOtherKeys函数）

         /// <summary>
         /// 屏蔽数字textbox的其他字符串
         /// </summary>
         /// <param name="sender"></param>
         /// <param name="e"></param>
         public virtual void tBoxNumbers_KeyDown(object sender, KeyEventArgs e)
         {
             e.SuppressKeyPress = true;

             switch (e.KeyCode)
             {
                 case Keys.D0:
                 case Keys.D1:
                 case Keys.D2:
                 case Keys.D3:
                 case Keys.D4:
                 case Keys.D5:
                 case Keys.D6:
                 case Keys.D7:
                 case Keys.D8:
                 case Keys.D9:
                 case Keys.NumPad0:
                 case Keys.NumPad1:
                 case Keys.NumPad2:
                 case Keys.NumPad3:
                 case Keys.NumPad4:
                 case Keys.NumPad5:
                 case Keys.NumPad6:
                 case Keys.NumPad7:
                 case Keys.NumPad8:
                 case Keys.NumPad9:
                 case Keys.Back:
                 case Keys.OemPeriod:
                 case Keys.Delete:
                 case Keys.Decimal:
                     e.SuppressKeyPress = false;
                     break;
                 default:
                     break;
             }
         }

         public virtual void tBoxNumbers_KeyPress(object sender, KeyPressEventArgs e)
         {
             TextBox tBox = sender as TextBox;
             char c = e.KeyChar;

             if (c.ToString().Equals("."))
             {
                 if (tBox.Text.Length <= )
                     e.Handled = true;           //小数点不能在第一位
                 else
                 {
                     float f;
                     float oldf;
                     bool b1 = false, b2 = false;
                     b1 = float.TryParse(tBox.Text, out oldf);
                     b2 = float.TryParse(tBox.Text + e.KeyChar.ToString(), out f);
                     if (b2 == false)
                     {
                         if (b1 == true)
                             e.Handled = true;
                         else
                             e.Handled = false;
                     }
                 }
             }
         }

         /// <summary>
         /// 屏蔽数字textbox的其他字符串
         /// </summary>
         /// <param name="tbox">要屏蔽的textbox</param>
         public virtual void ShieldNumberTextBoxOtherKeys(TextBox tbox)
         {
             tbox.ImeMode = ImeMode.Disable;
             tbox.KeyDown += tBoxNumbers_KeyDown;
             tbox.KeyPress += tBoxNumbers_KeyPress;
         }

         #endregion