I am building a dll, which references a second dll. I have added the second dll as a reference in the first dll\'s project by going to Properties > Common Properti
Right click on the project you created the dll and the new referencing project, then select properties. Under Application, check the target framework and verify that both have the same framework, some dll projects tend to select 'client profile' version of the framework by default, which tend to give the error you are having now..
Let me know if this is not the issue..