System.MissingMethodException: 找不到方法:

This is a problem which can occur when there is an old version of a DLL still lingering somewhere around.
Make sure that the latest assemblies are deployed and no duplicated older assemblies are hiding in certain folders.
Your best bet would be to delete every built item and rebuild/redeploy the entire solution.

http://stackoverflow.com/questions/8058832/system-missingmethodexception-method-not-found

错误原因：项目引用的dll版本不对导致的