The CLR Type '{0}' could not be loaded during service compilation. Verify that this type is either defined in a source file ...

The CLR Type '{0}' could not be loaded during service compilation. Verify that this type is either defined in a source file located in the application's \\App_Code directory, contained in a compiled assembly located in the application's \\bin directory, or present in an assembly installed in the Global Assembly Cache. Note that the type name is case-sensitive and that the directories such as \\App_Code and \\bin must be located in the application's root directory and cannot be nested in subdirectories.