need an example for Entity Framework when registering saga repositories with autofac - autofac

Question

The masstransit documentation has an example for NHiberbate, does anyone have the same example, but using entity framework (SagaDbContextFactory,SagaDbContext) instead of NHibernate
// do not forget registering saga repositories (example for NHibernate)
var mappings = mappingsAssembly
.GetTypes()
.Where(t => t.BaseType != null && t.BaseType.IsGenericType &&
(t.BaseType.GetGenericTypeDefinition() == typeof(SagaClassMapping<>) ||
t.BaseType.GetGenericTypeDefinition() == typeof(ClassMapping<>)))
.ToArray();
builder.Register(c => new SqlServerSessionFactoryProvider(connString, mappings).GetSessionFactory())
.As<ISessionFactory>()
.SingleInstance();
builder.RegisterGeneric(typeof(NHibernateSagaRepository<>))
.As(typeof(ISagaRepository<>));

Answer 1

I've registered mine like this:
builder.RegisterAssemblyTypes(typeof(SomeType).Assembly).AsImplementedInterfaces().AsSelf();
builder.RegisterGeneric(typeof(SagaRepository<,>)).As(typeof(ISagaRepository<,>));
builder.RegisterGeneric(typeof(SagaDbContext<,>));
And then implemented the SagaRepository interface:
internal class SagaRepository<TSaga, TSagaClassMapping> : EntityFrameworkSagaRepository<TSaga>, ISagaRepository<TSaga, TSagaClassMapping>
where TSaga : class, ISaga where TSagaClassMapping : SagaClassMapping<TSaga>, new()
{
public SagaRepository(
IWorkerConfiguration workerConfiguration)
: base(() => new SagaDbContext<TSaga, TSagaClassMapping>(workerConfiguration.ConnectionStrings["SagaRepository"]))
{
}
}
For the mappings I use a base class:
internal abstract class BaseInstanceStateMap<TInstance> : SagaClassMapping<TInstance>, IInstanceStateMap<TInstance> where TInstance : BaseSagaInstance
{
protected BaseInstanceStateMap()
{
this.Property(x => x.CorrelationId);
this.Property(x => x.CurrentState).HasMaxLength(64);
this.Property(x => x.Initiated).HasColumnType("datetime2").IsRequired();
this.Property(x => x.Created).HasColumnType("datetime2").IsRequired();
this.Property(x => x.StateChanged).HasColumnType("datetime2").IsOptional();
}
}
Which I then inherit for each of my mappings:
internal class ProductIndexingStateMap : BaseInstanceStateMap<ProductIndexingSagaInstance>
{
public ProductIndexingStateMap()
{
this.Property(x => x.ProductId);
this.Property(x => x.ProductCorrelation);
this.Property(x => x.EncryptedConnectionString);
}
}

Answer 2

You actually can register EntityFrameworkSagaRepository<T> as generic but it will require you to register one DbContext. If you use SagaDbContext - you cannot have more than one saga in your application. The only way to go there is to bind custom repository implementation and SagaDbContext via generic type parameters, this is what #slinzerthegod is doing in his example.
You can also create your own context that will register all types. For example:
public class AssemblyScanningSagaDbContext : DbContext
{
readonly Assembly _mappingAssembly;
public AssemblyScanningSagaDbContext(Assembly mappingAssembly, string nameOrConnectionString)
: base(nameOrConnectionString)
{
_mappingAssembly = mappingAssembly;
}
public AssemblyScanningSagaDbContext(Assembly mappingAssembly, ObjectContext objectContext, bool dbContextOwnsObjectContext)
: base(objectContext, dbContextOwnsObjectContext)
{
_mappingAssembly = mappingAssembly;
}
public AssemblyScanningSagaDbContext(Assembly mappingAssembly, DbConnection existingConnection, bool contextOwnsConnection)
: base(existingConnection, contextOwnsConnection)
{
_mappingAssembly = mappingAssembly;
}
public AssemblyScanningSagaDbContext(Assembly mappingAssembly, string nameOrConnectionString, DbCompiledModel model)
: base(nameOrConnectionString, model)
{
_mappingAssembly = mappingAssembly;
}
public AssemblyScanningSagaDbContext(Assembly mappingAssembly, DbConnection existingConnection, DbCompiledModel model, bool contextOwnsConnection)
: base(existingConnection, model, contextOwnsConnection)
{
_mappingAssembly = mappingAssembly;
}
protected AssemblyScanningSagaDbContext(Assembly mappingAssembly)
{
_mappingAssembly = mappingAssembly;
}
protected AssemblyScanningSagaDbContext(Assembly mappingAssembly, DbCompiledModel model)
: base(model)
{
_mappingAssembly = mappingAssembly;
}
protected override void OnModelCreating(DbModelBuilder modelBuilder) =>
modelBuilder.Configurations.AddFromAssembly(_mappingAssembly);
}
If you have such class, you can do the following:
builder.Register(c => new AssemblyScanningSagaDbContext(typeof(MySagaMapping).Assembly,
connectionString).As<DbContext>();
builder.RegisterGeneric(typeof(EntityFrameworkSagaRepository<>))
.As(typeof(ISagaRepository<>))
.SingleInstance();
builder.RegisterStateMachineSagas(typeof(MySaga).Assembly);
Autofac is able to compose a factory delegate automatically and will inject it to the repository constructor.
Here is the scanning context as gist.