Entity Framework Code First : Setting up One-To-One foreign key association using Annotations

ef-code-first, entity-framework, entity-framework-4.1

Solution

I think the foreignKey should be Id, not StandardRack_id. Also, you should use virtual, in order to be able to use lazy loading.

This works for me

using System.ComponentModel.DataAnnotations;
using System.Data.Entity;

namespace Racks
{

    public class StandardRack
    {
        public int Id { get; set; }
        public virtual StandardRelay StandardRelay { get; set; }
    }

    public class StandardRelay
    {
        public int Id { get; set; }

        public int StandardRack_Id { get; set; }

        [ForeignKey("Id")]
        [Required]
        public virtual StandardRack StandardRack { get; set; }
    }

    public class Context : DbContext
    {
        static Context()
        {
            Database.SetInitializer<Context>(null);
        }

        public DbSet<StandardRack> StandardRacks { get; set; }
        public DbSet<StandardRelay> StandardRelays { get; set; }

    }

    class Program
    {
        static void Main(string[] args)
        {
            var context = new Context();
            context.Database.Delete();
            context.Database.Create();

            var standardRack = new StandardRack();
            standardRack.StandardRelay = new StandardRelay();

            context.StandardRacks.Add(standardRack);
            context.SaveChanges();
        }
    }
}

Problem

I have following two Entities that I am trying to relate (one to one) using foreign key associations. ``` public class StandardRack { public int Id {get;set} public StandardRelay StandardRelay {get;set} } public class StandardRelay { public int Id {get;set} public int StandardRack_Id {get;set;} [Required][ForeignKey("StandardRack_Id")] public StandardRack StandardRack { get; set; } } ``` This throws ModelValidationException. Any ideas why such a seemingly simple one-to-one bidirectional relationship cannot be configured. Edit: Here is the Exception: System.Data.Entity.ModelConfiguration.ModelValidationException was caught Message=One or more validation errors were detected during model generation: System.Data.Edm.EdmAssociationEnd: : Multiplicity is not valid in Role 'StandardRelay_StandardRack_Source' in relationship 'StandardRelay_StandardRack'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be �*�. Source=EntityFramework StackTrace: at System.Data.Entity.ModelConfiguration.Edm.EdmModelExtensions.ValidateAndSerializeCsdl(EdmModel model, XmlWriter writer) at System.Data.Entity.ModelConfiguration.Edm.EdmModelExtensions.ValidateCsdl(EdmModel model) at System.Data.Entity.DbModelBuilder.Build(DbProviderManifest providerManifest, DbProviderInfo providerInfo) at System.Data.Entity.DbModelBuilder.Build(DbConnection providerConnection) at System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext internalContext) at System.Data.Entity.Internal.RetryLazy`2.GetValue(TInput input) at System.Data.Entity.Internal.LazyInternalContext.InitializeContext() at System.Data.Entity.Internal.InternalContext.Initialize() at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType) at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize() at System.Data.Entity.Internal.Linq.InternalSet`1.GetEnumerator() at System.Data.Entity.Infrastructure.DbQuery`1.System.Collections.Generic.IEnumerable.GetEnumerator() at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source) at TestApplication.MainWindow.Window_Loaded(Object sender, RoutedEventArgs e) in D:\RailwayProjects\RelayAnalysis\TestApplication\MainWindow.xaml.cs:line 33 InnerException:

Original source

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