I'm trying to use AjaxControlToolkit controls (specifically CalendarExtender and ComboBox), but am having problems with the ScriptManager control. I've got the ToolkitScriptManager at the top of the form, but when I load the page, I get this error:

Only one instance of a ScriptManager can be added to the page.

As soon as I removed the ScriptManager, I get this error:

Microsoft JScript runtime error: AjaxControlToolkit requires ASP.NET Ajax 4.0 scripts. Ensure the correct version of the scripts are referenced. If you are using an ASP.NET ScriptManager, switch to the ToolkitScriptManager in AjaxControlToolkit.dll.

I haven't added any other script managers anywhere else, and I've got the (.NET 3.5) DLL registered in GAC, and copies in the application's bin and _app_bin folders.

What's going on?

1 Answer 1


It's throwing the error because the <asp:ScriptManager> tag is most likely defined in your master page, causing two instances on the page you are trying to load.



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