Is it possible to deduplicate registration in unity?

Question

Consider interfaces:

public interface IOne{}
public interface ITwo{}
public interface IBoth : IOne, ITwo{}

And class

public         


        

Answer 1

Short answer: You can't. Long answer: You can write a custom container extension that does this kind of trick for you.

[TestMethod]
public void TestMethod1()
{
  var container = new UnityContainer().AddNewExtension();
  container.RegisterType();
  IThree three = container.Resolve();
  Assert.AreEqual("3", three.Three());
}

public class DeduplicateRegistrations : UnityContainerExtension
{
  protected override void Initialize()
  {
    this.Context.Registering += OnRegistering;
  }
  private void OnRegistering(object sender, RegisterEventArgs e)
  {
    if (e.TypeFrom.IsInterface)
    {
      Type[] interfaces = e.TypeFrom.GetInterfaces();
      foreach (var @interface in interfaces)
      {
        this.Context.RegisterNamedType(@interface, null);
        if (e.TypeFrom.IsGenericTypeDefinition && e.TypeTo.IsGenericTypeDefinition)
        {
          this.Context.Policies.Set(
            new GenericTypeBuildKeyMappingPolicy(new NamedTypeBuildKey(e.TypeTo)),
            new NamedTypeBuildKey(@interface, null));
        }
        else
        {
          this.Context.Policies.Set(
            new BuildKeyMappingPolicy(new NamedTypeBuildKey(e.TypeTo)),
            new NamedTypeBuildKey(@interface, null));
        }
      }
    }
  }
}
public class Both : IBoth
{
  public string One() { return "1"; }
  public string Two() { return "2"; }
  public string Three() { return "3"; }
}
public interface IOne : IThree
{
  string One();
}
public interface IThree
{
  string Three();
}
public interface ITwo
{
  string Two();
}
public interface IBoth : IOne, ITwo
{
}

You will need to fine-tune the extension in order to catch registration of interfaces like IDisposable or overwriting an already existing registration for a given interface.