可以应用到页面中的CheckBox上，通过为一组CheckBox指定同样的Key，让它们拥有类似单选按钮组(Radio Button Group)的行为，即用户只能选择组中的某一项。与单选按钮组不同的是，这个由CheckBox组成的单选按钮允许取消选择，即不选择组中的任意一项，而传统的单选按钮组则无法实现这个功能。
属性：
Key：隶属于同一群组的复选框，必须具有独一的键值。
TargetControlID：目标控件ID值。
实例代码：
<html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <title>Untitled Page</title></head><body> <form id="form1" runat="server"> <asp:ScriptManager ID="sm" runat="server" /> <table> <tr> <td colspan="2" > 外出旅游，您会携带‧‧‧ </td> </tr> <tr> <td style=" 165px" > 会携带 </td> <td style=" 165px" > 不会携带 </td> </tr> <tr> <td> <asp:CheckBox ID="chkBoxTakeCellPhone" runat="server" Text="手机" /><br /> <asp:CheckBox ID="chkBoxTakeCamera" runat="server" Text="相机" /><br /> <asp:CheckBox ID="chkBoxTakeMP3" runat="server" Text="MP3" /><br /> <asp:CheckBox ID="chkBoxTakeEraset" runat="server" Text="耳机" /><br /> <asp:CheckBox ID="chkBoxTakeNB" runat="server" Text="笔记本" /><br /> <asp:CheckBox ID="chkBoxTakeFlashDrive" runat="server" Text="随身听" /><br /> </td> <td> <asp:CheckBox ID="chkBoxNotTakeCellPhone" runat="server" Text="手机" /><br /> <asp:CheckBox ID="chkBoxNotTakeCamera" runat="server" Text="相机" /><br /> <asp:CheckBox ID="chkBoxNotTakeMP3" runat="server" Text="MP3" /><br /> <asp:CheckBox ID="chkBoxNotTakeEraset" runat="server" Text="耳机" /><br /> <asp:CheckBox ID="chkBoxNotTakeNB" runat="server" Text="笔记本" /><br /> <asp:CheckBox ID="chkBoxNotTakeFlashDrive" runat="server" Text="随身听" /> <br /> </td> </tr> <tr> <td colspan="2"> <hr /> </td> </tr> </table> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeTakeCellPhone" runat="server" TargetControlID="chkBoxTakeCellPhone" Key="CellPhone"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeNotTakeCellPhone" runat="server" TargetControlID="chkBoxNotTakeCellPhone" Key="CellPhone"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender>
<%-- 设定「相机」的互斥式复选框 --%>
<ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeTakeCamera" runat="server" TargetControlID="chkBoxTakeCamera" Key="PDA"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeNotTakePDA" runat="server" TargetControlID="chkBoxNotTakeCamera" Key="PDA"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <%-- 设定「MP3」的互斥式复选框 --%> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeTakeMP3" runat="server" TargetControlID="chkBoxTakeMP3" Key="MP3"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeNotTakeMP3" runat="server" TargetControlID="chkBoxNotTakeMP3" Key="MP3"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <%-- 设定「耳机」的互斥式复选框 --%> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeTakeEarset" runat="server" TargetControlID="chkBoxTakeEraset" Key="Eraset"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeNotTakeEarset" runat="server" TargetControlID="chkBoxNotTakeEraset" Key="Eraset"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <%-- 设定「笔记本」的互斥式复选框 --%> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeTakeNB" runat="server" TargetControlID="chkBoxTakeNB" Key="NB"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeNotTakeNB" runat="server" TargetControlID="chkBoxNotTakeNB" Key="NB"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeTakeFlashDrive" runat="server" TargetControlID="chkBoxTakeFlashDrive" Key="FlashDrive"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> <ajaxToolkit:MutuallyExclusiveCheckBoxExtender ID="mecbeNotTakeFlashDrive" runat="server" TargetControlID="chkBoxNotTakeFlashDrive" Key="FlashDrive"> </ajaxToolkit:MutuallyExclusiveCheckBoxExtender> </form></body></html>运行结果：
