如何在page_unload之后调试asp.net错误 - 无法在包含主页和许多用户控件的DropDownList中选择多个项目

vb.net。我们正在构建大量的动态控件，包括下拉列表。在Page_Unload事件完成后立即引发此错误，然后在global.asax Application_Error方法中捕获该错误。如何在page_unload之后调试asp.net错误 - 无法在包含主页和许多用户控件的DropDownList中选择多个项目

“不能在DropDownList中选择多个项目”

堆栈跟踪不告诉我任何关于什么控件实际上是导致此有用。我该如何调试？如果说我是在调试整个页面顺序步骤，我到激发Page_Unload事件的结束，以及错误被立即抛出/捕获在Global.asax：

堆栈是：

Cannot have multiple items selected in a DropDownList. 
Category: at System.Web.UI.WebControls.DropDownList.VerifyMultiSelect() 
    at System.Web.UI.WebControls.ListControl.RenderContents(HtmlTextWriter writer) 
    at System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) 
    at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
    at ASP.productsearch_aspx.__RenderpnlGrid(HtmlTextWriter __w, Control parameterContainer) 
    at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
    at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
    at System.Web.UI.WebControls.WebControl.RenderContents(HtmlTextWriter writer) 
    at System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) 
    at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
    at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
    at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
    at System.Web.UI.Control.Render(HtmlTextWriter writer) 
    at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
    at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
    at System.Web.UI.UpdatePanel.RenderChildren(HtmlTextWriter writer) 
    at System.Web.UI.UpdatePanel.Render(HtmlTextWriter writer) 
    at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
    at System.Web.UI.PageRequestManager.RenderFormCallback(HtmlTextWriter writer, Control containerControl) 
    at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
    at System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) 
    at System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) 
    at System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) 
    at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) 
    at System.Web.UI.HtmlFormWrapper.System.Web.UI.IHtmlForm.RenderControl(HtmlTextWriter writer) 
    at System.Web.UI.PageRequestManager.RenderPageCallback(HtmlTextWriter writer, Control pageControl) 
    at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
    at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
    at System.Web.UI.Page.Render(HtmlTextWriter writer) 
    at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
    at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
    at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

来源

2014-01-08 TheRedDwarf

尝试为System.Web.HttpException设置中断（例外对话框http://msdn.microsoft.com/en-us/library/h22dk1y6.aspx中有一个“查找...”按钮）。应用此设置后，调试程序应在抛出异常时停止（在System.Web.UI.WebControls.DropDownList.VerifyMultiSelect方法中）。在观察窗口中，您应该能够评估this并检查它所指的控件。

来源

2014-01-09 09:36:21 lowleveldesign

谢谢，但这并没有帮助。我确定System.Web.HttpException的异常被捕获，但是如果我在global.asax中有一个断点 - application_Error（），调试器只捕获它。届时，它给我的细节就是我上面粘贴的内容。 – TheRedDwarf

确保在VS中的“调试”选项“只是我的代码”复选框未选中，然后重试。 – lowleveldesign

如何在page_unload之后调试asp.net错误 - 无法在包含主页和许多用户控件的DropDownList中选择多个项目

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