Question

I’ve been trying to implement the Repository pattern using EntityFramework5. I already got the basics to work. My repositories are being loaded only when necessary and the data is being inserted/updated/retrieved in the database as it should.
The problem is: I can’t get the tables with mapping to be correctly created, or even created at all.
I’ve been reading some articles online, even here, talking about ways to work with mapped tables and create them in the database, but I haven’t succeed. Hands my question here.

How do I get it to work in my scenario?

I’ll explain what I’m doing so far:

This method below is overriden to, supposedly, create the mappings and tables.

PS: Generics.InvokeGenericMethod is a method I created and it’s working. It does what it says 🙂

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        foreach (Type entityType in Repositories.Keys)
        {
            //Invokes the Entity method from DbModelBuilder injecting the class type.
            Generics.InvokeGenericMethod(modelBuilder, typeof(DbModelBuilder), entityType, "Entity", null);
        }

        foreach (GaiaEntityConfiguration config in EntityConfigurations)
        {
            //Defines each mapping existing in the context
            config.SetConfiguration(modelBuilder);
        }
    }

The part that is not working is where I use SetConfiguration. SetConfiguration is a method I created for each class added to the context that has mapping, have that mapping mirrored to the database.

Here’s one example (in this case a recipient has many messages and messages have many recipients / many-to-many association):

PS: I left the commented code so you can see one other approach I tried.

    public RecipientEntityConfiguration()
    {
        this.LeftKey = "RecipientId";
        this.RightKey = "MessageId";
        this.Schema = "Hermes";
        this.TableName = "RecipientMessage";
    }

    public override void SetConfiguration(DbModelBuilder modelBuilder)
    {
        //EntityTypeConfiguration<Recipient> entityTypeConfiguration = new EntityTypeConfiguration<Recipient>();

        //entityTypeConfiguration
        //    .HasMany<Message>(r => r.Messages)
        //    .WithMany(m => m.Recipients)
        //    .Map(mr =>
        //    {
        //        mr.MapLeftKey(this.LeftKey);
        //        mr.MapRightKey(this.RightKey);
        //        mr.ToTable(this.TableName, this.Schema);
        //    });
        modelBuilder.Entity<Recipient>()
            .HasMany<Message>(r => r.Messages)
            .WithMany(m => m.Recipients)
            .Map(mr =>
            {
                mr.MapLeftKey(this.LeftKey);
                mr.MapRightKey(this.RightKey);
                mr.ToTable(this.TableName, this.Schema);
            });
        //modelBuilder.Configurations.Add<Recipient>(entityTypeConfiguration);
    }

When this.Database.Initialize(false); is called I get this error:

Value cannot be null.
Parameter name: key

StackTrace:

   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
   at System.Collections.Generic.Dictionary`2.TryGetValue(TKey key, TValue& value)
   at System.Data.Entity.ModelConfiguration.Configuration.Mapping.SortedEntityTypeIndex.Add(EdmEntitySet entitySet, EdmEntityType entityType)
   at System.Data.Entity.ModelConfiguration.Configuration.Mapping.EntityMappingService.Analyze()
   at System.Data.Entity.ModelConfiguration.Configuration.Mapping.EntityMappingService.Configure()
   at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.ConfigureEntityTypes(DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
   at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.Configure(DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
   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.Database.Initialize(Boolean force)
   at Gaia.Repository.GaiaContext..ctor(GaiaContextConfiguration config) in E:\Gaia\Gaia.Repository\GaiaContext.cs:line 37
   at Hermes.HMail.SendMessage(Int64 sender, Int64[] toUsers, String subject, String content, FileStream attachment) in G:\Gaia\Hermes\HMail.cs:line 78
   at Gaia.Controllers.ApplicationController.Test() in G:\Gaia\Gaia\Controllers\ApplicationController.cs:line 18
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ActionMethodDispatcher.<>c__DisplayClass1.<WrapVoidAction>b__0(ControllerBase controller, Object[] parameters)
   at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
   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.<>c__DisplayClass15.<InvokeActionMethodWithFilters>b__12()
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)

Any ideas?

Thanks.

Answer 1

First of all, I figured out in EF Book pg.57, that any in-line configurations, should appears only after all configurations added to modelbuilder. Checks your code.

Next, try this version of code, for automatiс adding mapping to modelbuilder.
The goal is to remove calls from EntityTypeConfigurations and use pure method of adding configurations to context. Move your code from SetConfiguration to constructor and try to use my version. It’s worked for me as well.

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
     var entityMapTypes = assembly.GetTypes().Where(
         (t => t.BaseType != null && t.BaseType.IsGenericType && 
               t.BaseType.GetGenericTypeDefinition() == typeof(EntityTypeConfiguration<>)));

     foreach (var mapType in entityMapTypes)
     {
         dynamic configurationInstance = Activator.CreateInstance(mapType);
         modelBuilder.Configurations.Add(configurationInstance);
     }
}