Error MSB3541: Files has invalid value

Try to search the entire solution for the value and remove it from where it occurs, and then delete the obj folder from your project. When you build again it should work.

The obj folders are hidden in Visual Studio. You can see them with a file explorer.

Delete the obj folder within your project and it will fix the issue.

though it is very old question but I would like to add an answer here. when you work with multiple developer in visual studio you should git ignore obj folder, .suo,.sln etc which is only holding the visual studio information user based.

refer to this SO question