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Error "Cannot have multiple items selected in a DropDownList" after clicking the Setting button on the Admin->Content Type->Page Types-Settings

Eric
Eric
Vote:
 

We get this error when trying to access page setting from within the Admin area.

Error "Cannot have multiple items selected in a DropDownList" after clicking the Setting button on the Admin->Content Type->Page Types-Settings

Cannot have multiple items selected in a DropDownList.

[HttpException (0x80004005): Cannot have multiple items selected in a DropDownList.]
   System.Web.UI.WebControls.DropDownList.VerifyMultiSelect() +96
   System.Web.UI.WebControls.ListControl.RenderContents(HtmlTextWriter writer) +9719093
   System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) +32
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +128
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +13
   System.Web.UI.Control.Render(HtmlTextWriter writer) +12
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   ASP.episerver_cms_admin_contenttypeinformation_ascx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in C:\Code\SVN\trunk\MVC\Mosaic\EPiServer\CMS\Admin\ContentTypeInformation.ascx:14
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +268
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +13
   System.Web.UI.Control.Render(HtmlTextWriter writer) +12
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   ASP.episerver_cms_admin_editpagetypesettings_aspx.__RenderGeneralSettings(HtmlTextWriter __w, Control parameterContainer) in c:\TempASP.NETFiles\vs\d578a7e3\dc62f13d\App_Web_t5m1fsje.0.cs:0
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +268
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +13
   System.Web.UI.WebControls.WebControl.RenderContents(HtmlTextWriter writer) +12
   System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) +32
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +128
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +13
   System.Web.UI.WebControls.WebControl.RenderContents(HtmlTextWriter writer) +12
   System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) +32
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +128
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +13
   System.Web.UI.Control.Render(HtmlTextWriter writer) +12
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +128
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +13
   System.Web.UI.Control.Render(HtmlTextWriter writer) +12
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +128
   System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +106
   System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +32
   System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) +53
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +40
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +128
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +13
   System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +32
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   ASP.episerver_cms_masterpages_episerverui_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in C:\Code\SVN\trunk\MVC\Mosaic\EPiServer\CMS\MasterPages\EPiServerUI.Master:10
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +268
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +13
   System.Web.UI.Control.Render(HtmlTextWriter writer) +12
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +128
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +13
   System.Web.UI.Page.Render(HtmlTextWriter writer) +29
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +66
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1303
#178205
May 04, 2017 15:46
Eric
Eric
Vote:
 

We are still having this issue after almost four years.

#269425
Jan 04, 2022 21:11
Ynze
Ynze
Vote:
 

The error means that the rendered DropDownList object has two items with selected="true" which is not allowed. The template selector is the only dropdown I can find in that page. The template selector items are generated automatically depending on your controllers. If this issue happens for all page types then it's likely to be a case of duplicate default templates being registered. Assuming you're using MVC, look for Controllers that are using the [TemplateDescriptor(Inherited = true)] attribute in your code. Then if you have multiple of them try renaming one using the Name="myname" parameter of the TemplateDescriptor attribute.

If you want to dive deeper you can use something like the ITemplateRepository service to get all the registered templates and inspect them for duplicates.

For reference this is what the template selector looks like:

Hope this helps

#272637
Feb 21, 2022 5:40
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