Property name in a type must be unique

Question

I am using Entity Framework 5 and I have the following entities:

public class User {
  public Int32 Id { get; set; }
  public String Username { get; set; }    
          


        

Answer 1

MapKey is only used if your foreign key column is not exposed as a property in your model. But in your case it is - as property Claim.Id. In that case you must use HasForeignKey instead of MapKey:

HasRequired<User>(x => x.User)
    .WithMany(y => y.Claims)
    .HasForeignKey(x => x.Id);

Answer 2

In addition to Slauma's answer

HasForeignKey is not available for 1:1, if you still need it you can simply use WithMany without parameters

HasRequired<User>(x => x.User).WithMany().HasForeignKey(x => x.Id);
HasRequired(x => x.City).WithMany().HasForeignKey(x => x.CityId);

Answer 3

This may happen also when there is a mismatch in the type of the referencing property. For example:

public string TipId { get; set; }

instead of

public int TipId { get; set; }