Property name in a type must be unique

c#, entity-framework

Solution

`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);

Problem

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; } public virtual ICollection<CLaim> CLaims { get; set; } } public class Claim { public Int32 Id { get; set; } public String Type { get; set; } public String Value { get; set; } public virtual User User { get; set; } } ``` A few notes about these entities: - In User entity the Id is the PK; - In Claim entity the Id is a FK and is equal to User.Id; - In Claim entity the PK is composite from (Id, Type, Value) So I have the following SQL for these entities: ``` create table dbo.Users ( Id int identity not null constraint PK_Users_Id primary key clustered (Id), Username nvarchar (120) not null constraint UQ_Users_Username unique (Username) ); create table dbo.Claims ( Id int not null, [Type] nvarchar (200) not null, Value nvarchar (200) not null, constraint PK_Claims_Id_Type_Value primary key (Id, [Type], Value), ); alter table dbo.Claims add constraint FK_CLaims_Id foreign key (Id) references dbo.Users(Id) on delete cascade on update cascade; ``` Finally, the configuration of the entities are as follows: ``` internal class UserConfiguration : EntityTypeConfiguration<User> { internal UserConfiguration() : base() { ToTable("Users"); HasKey(x => x.Id); Property(x => x.Id).IsRequired().HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity); Property(x => x.Username).IsRequired().HasMaxLength(120); } } internal class ClaimConfiguration : EntityTypeConfiguration<Claim> { internal ClaimMapper() : base() { ToTable("Claims"); HasKey(x => new { x.Id, x.Type, x.Value }); Property(x => x.Id).IsRequired().HasDatabaseGeneratedOption(DatabaseGeneratedOption.None); Property(x => x.Type).IsRequired().HasMaxLength(200); Property(x => x.Value).IsRequired().HasMaxLength(200); HasRequired<User>(x => x.User).WithMany(y => y.Claims).Map(z => { z.MapKey("Id"); }); } } ``` THE PROBLEM: When I try to create a user I get the following error: Each property name in a type must be unique. Property name 'Id' was already defined. Does anyone knows what I might be doing wrong?

Original source