I got an error using ASP.NET Identity in my app.
Multiple object sets per type are not supported. The object sets \'Identity Users\' and \'Users\'
This issue can arise from using scaffolding to create a View. You probably did something like this: View > Add > New Scaffold Item... > MVC 5 View > [Model class: ApplicationUser].
The scaffolding wizard added a new line of code in your ApplicationDbContext class.
public System.Data.Entity.DbSet IdentityUsers { get; set; }
Now you have two DbSet properties of the same type which not only causes an exeptions to be thrown in the FindAsync() method but also when you try to use code-first migrations.
Be very careful when using scaffolding or even better don't use it.