Visual Studio 2010 cannot add existing item in C project

I have the source code and hope to add the file xxx.c to source files of the project created by Visual Studio 2010. However, the source file is still in the original location even if I right click add --->existing item. What is added is actually just a link. What is the simpe wa开发者_如何学JAVAy to adding the item (but not a link) to the project?

Copy the source file into the same folder along with your other source/project files using Windows Explorer. Then use Add -> Existing Item.