Error creating Expression in Biztalk 2010, Assembly reference error?

I am adding an Expres开发者_StackOverflow社区sion in Biztalk 2010, which is as follows;

msgSalesOrder_Complete=msgSalesOrder;

msgSalesOrder_Complete.Comment="Work Done";

But i am getting the Assembly Rerference missing error for msgSalesOrder_Complete.Comment.

How is msgSalesOrder_Complete defined?

If it's a message schema, then Comment must be a (properly) distinguished or promoted property. If it's a .NET class, then the Comment member must be visible to the BizTalk project.

Obviously, the BizTalk project must have a reference to the project where the type of msgSalesOrder_Complete is defined, but I'm assuming this is the case...