FilterTextBoxExtender
TargetControlID - 要执行文本过滤的TextBox ID
FilterType - 过滤类型，Numbers，LowercaseLetters(小写)，UpcaseLettes（大写）and Custom(default)
FilterMode-ValidChars(default) and InvalidChars(低版本中不存在次属性)，设置其中任意一个值时，FilterType必须为Custom，也就是说FilterType是同时可以设置两种类型（Custom和其中任意一中），具体可以参看例子
ValidChars-有效字符，FilterMode中必须有Custom
InvalidChars-无效字符，FliterMode中必须有Custom
FilterInterval-the default is 250ms
More Information of FilterTextBoxExtender
Demo>>>
1 <asp:ScriptManager ID="ScriptManager1" runat="server" />
2 <div>
3 <ajaxToolkit:FilteredTextBoxExtender ID="FilteredTextBoxExtender1" runat="server"
4 TargetControlID="TextBox1" FilterType="Numbers" ClientIDMode="Inherit">
5 </ajaxToolkit:FilteredTextBoxExtender>
6 <ajaxToolkit:FilteredTextBoxExtender ID="FilteredTextBoxExtender2" runat="server"
7 TargetControlID="TextBox2" FilterType="LowercaseLetters">
8 </ajaxToolkit:FilteredTextBoxExtender>
9 <ajaxToolkit:FilteredTextBoxExtender ID="FilteredTextBoxExtender3" runat="server"
10 TargetControlID="TextBox3" FilterType="Custom, Numbers" ValidChars="+-=/*().">
11 </ajaxToolkit:FilteredTextBoxExtender>
12 <table border="0">
13 <tr>
14 <td>
15 Only digits are allowed here:
16 </td>
17 <td>
18 <asp:TextBox ID="TextBox1" runat="server">
19 </asp:TextBox>
20 </td>
21 </tr>
22 <tr>
23 <td>
24 Only lower-case letters are allowed here:
25 </td>
26 <td>
27 <asp:TextBox ID="TextBox2" runat="server">
28 </asp:TextBox>
29 </td>
30 </tr>
31 <tr>
32 <td>
33 Only math symbols (+,-,*,/,=,.) and numbers:
34 </td>
35 <td>
36 <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
37 </td>
38 </tr>
39 </table>
额外还想补充点，该控件与验证控件不同的是，如果不符合的内容是无法输入的。