Ajax:FilteredTextBoxExtender

 <table width="400">        <tr>            <td>                <asp:Label ID="label1" runat="server" Text="Only Numbers" Width="150"></asp:Label>                <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>                <ajaxToolkit:FilteredTextBoxExtender ID="FilteredTextBoxExtender1" runat="server" TargetControlID="TextBox1" FilterType="Numbers" />            </td>        </tr>        <tr>            <td>                <asp:Label ID="label2" runat="server" Text="Uppercase Letter" Width="150"></asp:Label>                <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>                <ajaxToolkit:FilteredTextBoxExtender ID="FilteredTextBoxExtender2" runat="server"TargetControlID="TextBox2" FilterType="UppercaseLetters" />            </td>        </tr>        <tr>            <td>                <asp:Label ID="label3" runat="server" Text="Lowercase Letters" Width="150"></asp:Label>                <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>                <ajaxToolkit:FilteredTextBoxExtender ID="FilteredTextBoxExtender3" runat="server"TargetControlID="TextBox3" FilterType="lowercaseLetters" />            </td>        </tr>        <tr>            <td>                <asp:Label ID="label4" runat="server" Text="Custom numbers" Width="150"></asp:Label>                <asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>                <ajaxToolkit:FilteredTextBoxExtender ID="FilteredTextBoxExtender4" runat="server"TargetControlID="TextBox4" FilterType="Custom, Numbers" ValidChars="+-=/*()." />            </td>        </tr>
         <tr>            <td>                <asp:Label ID="label4" runat="server" Text="Custom numbers" Width="150"></asp:Label>                <asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>              <ajaxToolkit:FilteredTextBoxExtender ID="ftxtAcdD_MHTCET_Tot" runat="server" TargetControlID="txtbox1" FilterType="Custom" ValidChars="0123456789"; />            </td>        </tr>    </table>