Deleting DLL from bin directory causes compile errors in ASP.NET MVC

i have a project say MyProject. It is an asp.net MVC project. In bin directory, i have deleted a DLL named MyProject.dll. Now when i try to build the project, i am getting following error.

The name MyProject does not exist in the current context.

In my view files and controller, there are a lot of code like

MyProject.Models;

or

MyProject.Utility.IsValidEmail(email);

how to build this solution?

obviously, the MyProject.dll is the compiled code of the MyProject instance. WHy did you delete it?