A bug in X.Studio previously corrupted .csproj files by partially or completely deleting the xml code in the .csproj file. As of the 5.1.4 stable release on July 15th, this bug has been fixed; but in many cases the project file has to be repaired manually, as described below:
- Create a brand new Xamarin.Android application project, set all the project properties to match your old project, and add all of your resources, source files, etc. back into the project.