Get cannot find the master page error

I have added master page to the project. Although I can successfully run the page, it doesn't switch to design view.

It gives me errors :

1)Cannot find the master page. 2)No build providers specified for the extension (They are added in both the applications and machine's web.config). 3)Can't switch to design view. 开发者_如何学GoGet an error cannot find a User Control. The UserControl is an dll, provided by the client for searching employees.

Just Clean the Solutions of Project.And Buid the Application.Again Re-Build the Application.

Ctrl+Shift+B  --> To Build an Solution
Go to Build --> Clean Solution

Some times the Visual Studio get the intellisense problems.This is may also Like that i think otherwise there is nothing.