I had similar problems. In Visual Studio I didn't find a good way to check the file encoding and didn't want to save all the files just to make sure they have the right encoding.

I opened those files in Notepad++. There is the Encoding tab where you can check file encoding and also change it from the files it is needed. That fixed the problem for me and it was quite fast to check all files with it. Also set the configuration in VS so that documents is saved as Unicode when data cannot be saved in codepage as mentioned in the other aswer.