Asp.net Identity Validation Error

Question

Your code does't show this, but from the errors you are getting I assume that you are overriding OnModelCreating.This is where IdentityDbContext<ApplicationUser> configure the entity framework mappings. This means that if you want to override OnModelCreating you need to either call the base or you must do the mapping yourself.

So either this:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);

    // your stuff here
}

Or you do the mapping:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<IdentityUserLogin>().HasKey<string>(l => l.UserId);
    modelBuilder.Entity<IdentityRole>().HasKey<string>(r => r.Id);
    modelBuilder.Entity<IdentityUserRole>().HasKey(r => new { r.RoleId, r.UserId });
}

If you don't want to call base.OnModelCreating and want to do your own mapping, your mapping should look like this:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<IdentityRole>().HasKey<string>(r => r.Id).Property(p => p.Name).IsRequired();
    modelBuilder.Entity<IdentityUserRole>().HasKey(r => new { r.RoleId, r.UserId });
    modelBuilder.Entity<IdentityUserLogin>().HasKey(u => new {u.UserId, u.LoginProvider, u.ProviderKey});
}

If you put the key for IdentityUserLogin only on UserId, you get DbEntityValidationExceptions when using the default google login.

The take away is that you cannot have an empty OnModelCreating

Good

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
  base.OnModelCreating(modelBuilder);
  // your stuff here
}

Bad

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
  // base.OnModelCreating(modelBuilder);
  // your stuff here
}