intellisense not working in vs2012

Question

I have a solution with 50 projects. It was written in VS2010 and later converted to VS2012. All intelisense work great, except for markup intelisense (Aspx, ascx..) for "telerik" tag and custom created controls. asp tag works fine

If I create a new project and reference telerik, then intelisense works, so I guess there's something wrong with my project. I tried to compare web.configs side by side. They look identical. Assemblies look identical as well. My web.config looks like this:

<controls>
        <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add tagPrefix="asp" namespace="System.Web.UI.WebControls" assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add tagPrefix="asp" namespace="System.Web.UI.DataVisualization.Charting" assembly="System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
        <add tagPrefix="telerik" namespace="Telerik.Web.UI" assembly="Telerik.Web.UI" />
        <add tagPrefix="custom" src="src/to/control" tagName="myControl1" />
        <add tagPrefix="custom" src="path...." tagName="myControl2" />
      </controls>

Things I've tried:
1. Tools->Options->Text Editor->C# (or All Languages)->General enable Auto List Members and Parameter Information in right hand side pane.
2.Tools->Import and Export settings->Reset all settings.
3.delete data from Roaming\Microsoft\VisualStudio\11.0\ReflectedSchemas
4. Delete cache in ProgramFiles\VisualStudio...
5. Reinstall visual studio
6. Run as administrator

If you have any clues or possible solutions, please let me know.

Answer 1

I had this happen in Visual Studio 2013. Here's what I did to get Intellisense back:

1. Add a reference in your project to Telerik.Web.Design.dll.
2. Save your project.
3. Reload your project in the IDE. (I restarted VS, just in case.)

HTH!

Answer 2

Register your Telerik.Web.UI.dll in Gac and this solution work for me.