error:Could not load file or assembly 'System.Web.Http.WebHost, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
My project is builded by use asp.net MVC4,EF6.0, and .net framework4.5
The guy set up the server said that he already had .net framework4.5 there, but in the application pool I only could see 4.0 and when I put the published website project over there,show error about.
Doesn't anyone know what happen? how to solve it??????????