Could not load file or assembly. Help!

Hi all,
I got the error as shown in below, can anyone guide me how to solve it?
Server Error in '/dracula' Application.
Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Could not load file or assembly 'Microsoft.Data.Schema.Sql, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

Sou ...