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POEntity Framework 4 CTP 5 Self Referencing Many-to-Many
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  1. POEntity Framework 4 CTP 5 Self Referencing Many-to-Many
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    copied!<p>I have the following scenario in my database. It is a record of Studies and those studies have other studies as prerequisites. In my DB design, it looks like this: </p> <p><img src="https://i.stack.imgur.com/negZP.png" alt="self referencing many to many"></p> <p>And my code looks something like this:</p> <pre><code>public class Study { public int ID { get; set; } public string Topic { get; set; } public byte TypeID { get; set; } public virtual StudyType Type { get; set; } public bool Deprecated { get; set; } public virtual ICollection&lt;Study&gt; Prerequisites { get; set; } } public class StudyType { public byte ID { get; set; } public string Name { get; set; } public virtual ICollection&lt;Study&gt; Studies { get; set; } } public class MyContext : DbContext { public DbSet&lt;Study&gt; Studies { get; set; } public DbSet&lt;StudyType&gt; StudyTypes { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity&lt;Study&gt;() .HasMany(p=&gt;p.Prerequisites) .WithMany().Map(ps =&gt; { ps.ToTable("Prerequisites"); ps.MapLeftKey(x=&gt;x.ID,"StudyID"); ps.MapRightKey(y=&gt;y.ID,"PrerequisiteID"); }); } </code></pre> <p>I'm not super good at the EF syntax, but from what I've found Googling, that seems like it should work. Instead, I get <code>Sequence contains more than one matching element</code>.</p> <p>I found this, but since the entity is referencing itself, I can't exactly rename the key field in only one of the tables: <a href="http://social.msdn.microsoft.com/Forums/eu/adonetefx/thread/745a2c4f-cb66-41ad-9524-15aa198c40c7" rel="noreferrer">http://social.msdn.microsoft.com/Forums/eu/adonetefx/thread/745a2c4f-cb66-41ad-9524-15aa198c40c7</a></p> <p>Anybody help me through this?</p> <p><strong>EDIT</strong></p> <p>Here is the full stack trace of the exception:</p> <p>It executes on a line of LINQ: <code>var x = from s in db.Studies select s;</code> </p> <pre><code>Server stack trace: at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate) at System.Data.Entity.ModelConfiguration.Configuration.Properties.Navigation.ManyToManyAssociationMappingConfiguration`2.Configure(DbAssociationSetMapping associationSetMapping) at System.Data.Entity.ModelConfiguration.Configuration.Properties.Navigation.NavigationPropertyConfiguration.Configure(DbDatabaseMapping databaseMapping) at System.Data.Entity.ModelConfiguration.Utilities.IEnumerableExtensions.Each[T](IEnumerable`1 ts, Action`1 action) at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.ConfigureAssociationMappings(DbDatabaseMapping databaseMapping) at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.Configure(DbEntityTypeMapping entityTypeMapping, DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest) at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.Configure(DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest) at System.Data.Entity.ModelConfiguration.ModelBuilder.Build(DbProviderManifest providerManifest, DbProviderInfo providerInfo, Boolean validateModel) at System.Data.Entity.ModelConfiguration.ModelBuilder.Build(DbConnection providerConnection) at System.Data.Entity.Internal.LazyInternalContext.CreateModel() at System.Lazy`1.CreateValue() Exception rethrown at [0]: at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate) at System.Data.Entity.ModelConfiguration.Configuration.Properties.Navigation.ManyToManyAssociationMappingConfiguration`2.Configure(DbAssociationSetMapping associationSetMapping) at System.Data.Entity.ModelConfiguration.Configuration.Properties.Navigation.NavigationPropertyConfiguration.Configure(DbDatabaseMapping databaseMapping) at System.Data.Entity.ModelConfiguration.Utilities.IEnumerableExtensions.Each[T](IEnumerable`1 ts, Action`1 action) at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.ConfigureAssociationMappings(DbDatabaseMapping databaseMapping) at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.Configure(DbEntityTypeMapping entityTypeMapping, DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest) at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.Configure(DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest) at System.Data.Entity.ModelConfiguration.ModelBuilder.Build(DbProviderManifest providerManifest, DbProviderInfo providerInfo, Boolean validateModel) at System.Data.Entity.ModelConfiguration.ModelBuilder.Build(DbConnection providerConnection) at System.Data.Entity.Internal.LazyInternalContext.CreateModel() at System.Lazy`1.CreateValue() at System.Lazy`1.LazyInitValue() at System.Data.Entity.Internal.LazyInternalContext.InitializeContext() 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.get_Provider() at System.Linq.Queryable.Select[TSource,TResult](IQueryable`1 source, Expression`1 selector) at DataAccess.Sql.SqlStudyRepository.GetAll() in C:\Side Work\Rephidim Church\Tuchikos 2011\Program\DataAccess\Sql\SqlStudyRepository.cs:line 22 at API.Controllers.StudiesController.Index() in C:\Side Work\Rephidim Church\Tuchikos 2011\Program\API\Controllers\StudiesController.cs:line 24 at lambda_method(Closure , ControllerBase , Object[] ) at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) at System.Web.Mvc.ControllerActionInvoker.&lt;&gt;c__DisplayClass15.&lt;InvokeActionMethodWithFilters&gt;b__12() at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) </code></pre>
 

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