ajaxToolkit:ModalPopupExtender可以讓用戶模擬新開一個窗口，以下演示，就是在模擬新開窗口作多項選項的功能。 
 
演示例子中，是Repeater結合CheckBox進行多選，此功能實現，可以參考：http://www.jfrwli.cn/article/20096.html 

選擇的小圖片，它將要被ajaxToolkit:ModalPopupExtender使用，因為需要設為服務控件，添加runat="server"： 

復制代碼代碼如下:

<img id="ab" runat="server" style="margin-left: 5px; margin-bottom: 30px;" 
src="../Image/ab.gif" width="18" height="18" /> 

下面是Popup窗口的Html，不過Insus.NET已經省略了Repeater控件內的內容，你在應用時，需要添加的你自己的，還是就是btnSelected_Click事件。 

復制代碼代碼如下:

<asp:Panel ID="pnlPopupWindown" runat="server" Style="display: none; background-color: #ffffdd; 
border-width: 3px; border-style: solid; border-color: Gray; padding: 3px; width: 500px;"> 
<asp:Panel ID="Panel3" runat="server" Style="float: left; margin-bottom: 5px; cursor: move; 
background-color: #DDDDDD; border: solid 1px Gray; color: Black; height: 20px; 
width: 475px; text-align: center; line-height: 20px;"> 
郵件地址列表 
</asp:Panel> 
<asp:Panel ID="Panel4" runat="server" Style="float: right; margin-bottom: 5px; background-color: #DDDDDD; 
border: solid 1px Gray; color: Black; height: 20px; text-align: center; line-height: 20px;"> 
<asp:LinkButton ID="btnClose" runat="server" Style="margin-right: 4px; margin-left: 4px;" 
OnClientClick="return false;" Text="×" ForeColor="Red" ToolTip="Close" /> 
</asp:Panel> 
<div> 
<asp:Panel ID="Panel1" runat="server" ScrollBars="Vertical" Height="198px" Width="100%" 
BorderStyle="Solid" BorderWidth="1px" BorderColor="Gray"> 
<asp:Repeater ID="RepeaterEmailList" runat="server"> 
</asp:Repeater> 
</asp:Panel> 
<div style="height: 3px;"> 
</div> 
<asp:Panel ID="Panel2" runat="server"> 
<asp:Button ID="btnSelected" runat="server" OnClick="btnSelected_Click" Text="插入" 
CausesValidation="false" CssClass="button" /> 
</asp:Panel> 
</div> 
</asp:Panel> 
<ajaxToolkit:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="ab" 
PopupControlID="pnlPopupWindown" BackgroundCssClass="modalBackground" CancelControlID="btnClose" 
DropShadow="true" PopupDragHandleControlID="Panel3" /> 
<script type="text/javascript"> 
function setBodyHeightToContentHeight() { 
document.body.style.height = Math.max(document.documentElement.scrollHeight, document.body.scrollHeight) + "px"; 
} 
setBodyHeightToContentHeight(); 
$addHandler(window, "resize", setBodyHeightToContentHeight); 
</script> 

最后是CSS樣式： 

復制代碼代碼如下:

/*Modal Popup*/ 
.modalBackground 
{ 
background-color: Gray; 
filter: alpha(opacity=70); 
opacity: 0.7; 
}