I installed VS 2012 Ultimate and also ArcObjects WDK for MS .Net FW. Then I opened a .sln on the VS 2012 but got the Error below:
The "ValidateAddInXMLTask" task could not be loaded from the assembly ESRI.ArcGIS.AddIns.SDK, Version=10.2.0.0, Culture=neutral, PublicKeyToken=8fc3cc631e44ad86. Could not load file or assembly 'Microsoft.VisualStudio.Shell.9.0, Version=126.96.36.199, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified. Confirm that the <UsingTask> declaration is correct, that the assembly and all its dependencies are available, and that the task contains a public class that implements Microsoft.Build.Framework.ITask.
I checked the Registry Editor, and did see the item: ESRI.ArcGIS.AddIns.SDK.11, Version="10.2.0.0"
What should I do to debug it? Appreciate if you can help for this issue.