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Cannot have multiple items selected in a DropDownList
Message
From
06/06/2016 09:25:01
Michel Fournier
Level Extreme Inc.
Petit-Rocher, New Brunswick, Canada
 
 
To
All
General information
Forum:
ASP.NET
Category:
Other
Title:
Cannot have multiple items selected in a DropDownList
Environment versions
Environment:
VB 9.0
OS:
Windows 8.1
Network:
Windows 2008 Server
Database:
MS SQL Server
Application:
Web
Miscellaneous
Thread ID:
01637030
Message ID:
01637030
Views:
68
I have never had this one on the Web site. I got two errors like this morning:

"Cannot have multiple items selected in a DropDownList."

The stack trace gives this:

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 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.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer)
at System.Web.UI.HtmlControls.HtmlContainerControl.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.HtmlControls.HtmlContainerControl.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 Framework.WebForm.Render(HtmlTextWriter toHtmlTextWriter)
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)

It is unclear how a user was able to make two selections in a select HTML control, which comes from DropDownList ASP.NET control.

Anyone would have an idea what could be the trigger here?
Michel Fournier
Level Extreme Inc.
Designer, architect, owner of the Level Extreme Platform
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