An assembly (probably "{1}") must be rewritten using the code contracts binary rewriter (CCRewrite) because it is calling ...

An assembly (probably "{1}") must be rewritten using the code contracts binary rewriter (CCRewrite) because it is calling Contract.{0} and the CONTRACTS_FULL symbol is defined.  Remove any explicit definitions of the CONTRACTS_FULL symbol from your project and rebuild.  CCRewrite can be downloaded from http://go.microsoft.com/fwlink/?LinkID=169180. 
After the rewriter is installed, it can be enabled in Visual Studio from the project's Properties page on the Code Contracts pane.  Ensure that "Perform Runtime Contract Checking" is enabled, which will define CONTRACTS_FULL.