未在数据库中创建具有映射的表

我一直在尝试使用EntityFramework5实现存储库模式。我已经掌握了工作的基本知识。我的存储库仅在必要时加载，并且数据按预期在数据库中插入/更新/检索。问题是：我无法正确创建带有映射的表，甚至根本无法创建。我一直在网上阅读一些文章，甚至在这里，谈论使用映射表并在数据库中创建它们的方法，但我没有成功。在这里提出我的问题。

如何让它在我的方案中工作？

我将解释到目前为止我正在做的事情：

下面的此方法被覆盖以创建映射和表。

PS：Generics.InvokeGenericMethod是我创建的方法，它正在起作用。它说到做到:)

    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);
        }
    }

不工作的部分是我使用SetConfiguration的地方。SetConfiguration 是我为添加到具有映射的上下文中的每个类创建的方法，并将该映射镜像到数据库。

下面是一个示例（在本例中，收件人有许多邮件，而邮件具有许多收件人/多对多关联）：

PS：我留下了注释的代码，以便您可以看到我尝试的另一种方法。

    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);
    }

调用this.Database.Initialize(false);时，出现此错误：

Value cannot be null.
Parameter name: key

堆栈跟踪：

   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)

有什么想法吗？

谢谢。

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);
     }
}