Entity framework Validation errors has no key defined. Define the key for this EntityType

Question

I am getting this Entity Framework error when I try to save an object in my Database context. I have no idea where to start looking.

What could be happening here?

How can I isolate what the issue is?

Thanks.

{System.Data.Entity.ModelConfiguration.ModelValidationException: One or more validation errors were detected during model generation:

\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'Exception' has no key defined. Define the key for this EntityType.
\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'AssemblyName' has no key defined. Define the key for this EntityType.
\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'CultureInfo' has no key defined. Define the key for this EntityType.
\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'DateTimeFormatInfo' has no key defined. Define the key for this EntityType.
\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'IdentityReference' has no key defined. Define the key for this EntityType.
\tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'Exceptions' is based on type 'Exception' that has no keys defined.
\tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'AssemblyNames' is based on type 'AssemblyName' that has no keys defined.
\tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'CultureInfoes' is based on type 'CultureInfo' that has no keys defined.
\tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'DateTimeFormatInfoes' is based on type 'DateTimeFormatInfo' that has no keys defined.
\tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'IdentityReferences' is based on type 'IdentityReference' that has no keys defined.

   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.get_InternalContext()
   at System.Data.Entity.Internal.Linq.InternalSet`1.ActOnSet(Action action, EntityState newState, Object entity, String methodName)
   at System.Data.Entity.Internal.Linq.InternalSet`1.Add(Object entity)
   at System.Data.Entity.DbSet`1.Add(TEntity entity)
   at MVCDaemon.Controllers.AwardBadgesController.FromUnprocessedEvents() in Hobby Stuff\Hehe\Hehe.Daemon\Controllers\AwardBadgesController.cs:line 58}

and my other stuff:

DaemonDB.Tasks.Add(T);

and

public class DaemonDBContext : DbContext
    {
        public DaemonDBContext() : base("DefaultConnection") { }

        //Collections also in BaseDBContext:
        public DbSet<Badge> Badges { get; set; }
        public DbSet<BadgeGroup> BadgeGroups { get; set; }
        public DbSet<Event> Events { get; set; }

        //Collections only in DaemonDBContext
        public DbSet<EventCheckedForBadgeReward> EventCheckedForBadgeReward { get; set; }
        public DbSet<Task> Tasks { get; set; }
    }

and

public class Task
    {
        public int ID { get; set; }
        public string FriendlyTitle { get; set; }
        public DateTime TimeOfExecution { get; set; }
        public TimeSpan LengthOfExecution { get; set; }
        public Stopwatch StopWatch;
        public Exception ExceptionEncountered { get; set; }

        public Task() {
            TimeOfExecution = DateTime.Now;
        }

        public void StartStopwatch()
        {
            StopWatch = Stopwatch.StartNew();
            StopWatch.Start();
        }

        public void StopStopwatch()
        {
            StopWatch.Stop();
        }

        public string GetStatusAsFriendly()
        {
            return ExceptionEncountered == null ? "Success" : "Failed";
        }
    }

Answer 1

不得不在某些属性上使用[NotMapped]属性。