Getting “type or namespace name could not be found” but everything seems ok?

Question

I\'m getting a:

type or namespace name could not be found

error for a C# WPF app in VS2010. This area of code was compiling fine

Answer 1

Adding my solution to the mix because it was a bit different and took me a while to figure out.

In my case I added a new class to one project but because my version control bindings weren't set I needed to make the file writable outside of Visual Studio (via the VC). I had cancelled out of the save in Visual Studio but after I made the file writable outside VS I then hit Save All again in VS. This inadvertently caused the new class file to not be saved in the project..however..Intellisense still showed it up as blue and valid in the referencing projects even though when I'd try to recompile the file wasn't found and got the type not found error. Closing and opening Visual Studio still showed the issue (but if I had taken note the class file was missing upon reopening).

Once I realized this, the fix was simple: with the project file set to writeable, readd the missing file to the project. All builds fine now.