Question

The working IDE is Visual studio 2010 and the target Framework of the project is .NET4

I get the error Type 'System.Web.UI.ScriptManager' is not defined

after adding the ScriptManager component and building the project.

Actually i get the same error type after adding an UpdatePanel too.

The project has a reference to C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\System.Web.dll

Could you please tell me what is going on here?

As far as i saw, after creating a new new dummy web-project, i got no error after adding the script manager object on that. (So now i am 100% sure that the error has something to do with the configuration into my project).

By the way if try to add a reference to the System.Web.Extensions the IDE crashes!

Answer 1

You get the error Type 'System.Web.UI.ScriptManager' is not defined because you actually need a Reference to the System.Web.Extensions library, but you probably figured this out already. It seems strange though that your reference to System.Web seems to come from your Program Files instead of the GAC. This might be related to the crash you are getting.

Please try this:

• Close Visual Studio
• Open your web application’s .csproj file with a text editor (like
  NotePad++)
• Look for the ItemGroup node; this contains your project references
• Change your reference to System.Web to look like this: Reference Include="System.Web"
• Add an additional line: Reference Include="System.Web.Extensions"
• Save and Close
• Now open your project again in VS and see if it has helped