Nobot控件------拒绝机器人行为

功能：
    NoBot 控件可以为页面中的表单提供类似验证码而却无需任何用户操作的验证，以阻止机器人程序自动提交垃圾信息。
属性： 

1. ResponseMinimumDelaySeconds： 一个合理的客户端从开始接受页面到提交表单的时间间隔，单位为秒。在该时间段之内的提交将被认为是机器人所为。
2. CutoffWindowSeconds：指定一个统计同一客户端提交次数的窗口时间段，单位为秒。在该时间段之内的提交次数超过CutoffMaximumInstances所指定的值将被认为是机器人所为。
3. CutoffMaximumInstances：指定在窗口时间段内同一客户端最多的提交次数。在CutoffWindowSeconds所指定的时间段之内的提交次数超过该值将被认为是机器人所为。
4. OnGenerateChallengeAndResponse：指定GenerateChallengeAndResponse事件的处理函数。在该事件处理函数中我们可以设定强制浏览器执行的一段JavaScript以及其预期的执行结果。若浏览器的执行结果和预期结果不符，则本次提交将被认为是机器人所为。

实例代码：   
    前台代码：

 <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>


    <table cellSpacing="15">
                <tr>
                    <td>
                        <asp:Panel ID="panPersonalData" runat="server" Height="250px" Width="450px">
                            <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
                                <ContentTemplate>
                                    <table cellPadding="5">
                                        <tr>
                                            <td colspan="2" align="center" Class="lgHeader">
                                                <strong>个人资料</strong></td>
                                        </tr>
                                        <tr>
                                            <td style="width: 150px" class="header">
                                                姓名：</td>
                                            <td style="width: 300px">
                                                <asp:TextBox ID="txtName" runat="server" CssClass="content"></asp:TextBox></td>
                                        </tr>
                                        <tr>
                                            <td style="width: 150px" class="header">
                                                性别：</td>
                                            <td style="width: 300px">
                                                <asp:RadioButton ID="rdoMale" runat="server" GroupName="Gender"
                                                    Text="男" CssClass="content" Checked="True" />
                                                &nbsp;
                                                <asp:RadioButton ID="rdoFemale" runat="server" GroupName="Gender"
                                                    Text="女" CssClass="content" /></td>
                                        </tr>
                                        <tr>
                                            <td style="width: 150px" class="header">
                                                出生年份：</td>
                                            <td style="width: 300px">
                                                <asp:TextBox ID="txtBirthYear" runat="server" MaxLength="4" CssClass="content"></asp:TextBox>
                                            </td>
                                        </tr>
                                        <tr>
                                            <td style="width: 150px" class="header">
                                                家庭住址：</td>
                                            <td style="width: 300px">
                                                <asp:TextBox ID="txtAddress" runat="server" MaxLength="6" CssClass="content"></asp:TextBox>
                                            </td>
                                        </tr>
                                        <tr>
                                            <td align="center" colspan="2">
                                                <hr />
                                            </td>
                                        </tr>
                                    </table>
                                </ContentTemplate>
                                <Triggers>
                                    <asp:AsyncPostBackTrigger ControlID="btnRest" EventName="Click" />
                                </Triggers>
                            </asp:UpdatePanel>

                            <table width="100%">
                                <tr>
                                    <td align="center">
                                        <asp:Button ID="btnSubmit" runat="server" Text="确定" onclick="btnSubmit_Click" />
                                        &nbsp; &nbsp;
                                        <asp:Button ID="btnRest" runat="server" Text="取消" onclick="btnRest_Click" />
                                    </td>
                                </tr>
                            </table>
                        </asp:Panel>
                        <ajaxToolkit:DropShadowExtender ID="DropShadowExtender1" runat="server"
                            TargetControlID="panPersonalData"
                            Radius="25"
                            Rounded="true"
                            Opacity=".2"
                            TrackPosition="true">
                        </ajaxToolkit:DropShadowExtender>
                        <ajaxToolkit:NoBot ID="myNoBot" runat="server"  ResponseMinimumDelaySeconds="2"
                                CutoffWindowSeconds="60"
                                CutoffMaximumInstances="5"
/>
                    </td>
                    <td style="width: 350px">
                        <asp:UpdatePanel ID="upStatus" runat="server" UpdateMode="Conditional">
                            <ContentTemplate>
                                <asp:Literal ID="ltlStatus" runat="server"></asp:Literal>
                            </ContentTemplate>
                            <Triggers>
                                <asp:AsyncPostBackTrigger ControlID="btnSubmit" EventName="Click" />
                                <asp:AsyncPostBackTrigger ControlID="btnRest" EventName="Click" />
                            </Triggers>
                        </asp:UpdatePanel>
                    </td>
                </tr>
            </table>

    </form>

    后台代码：    

 protected void btnSubmit_Click(object sender, EventArgs e)
    }

运行结果：
        
    如果你在2秒内，又提交这份表单，则会提示如下图所示：