Question

I have multiple interfaces that my objects can implement. I am wondering if there is a way to “cascade” one extension method into another while using the same method name. I may be looking at this all wrong, but here is an example:

public interface IBaseDto
{
     int Id {get;set;}
     string CreatedByFullName {get;set;}
}

public interface IDocumentDto
{
     List<ContactDto> Subscriptions {get;set;}
}

public class ContactDto: IBaseDto
{
     public int Id {get;set;}
     public string CreatedByFullName {get;set;}
     public string FirstName {get; set}
     public string LastName {get;set;}
}

public class MeetingDto: IDocumentDto
{
     public int Id {get;set;}
     public string CreatedByFullName {get;set;}
     public List<ContactDto> Subscriptions {get;set;}
}

So, let’s say I want to convert the DTOs into entities using an extension method. An example would be MeetingDto.ToEntity();

I am trying to think if I can write part of the extension method for an IBaseDto, another for the IDocumentDto and then for each concrete implementations for just their own properties. When I call MeetingDto.ToEntity() it would first hit the meeting extension method and call the IDocumentDto version, fill in what it needed, and then the IDocumentDto would call the IBaseDto. I hope this makes sense.

UPDATE:

I came up with this and it works pretty well:

public static TBaseDto ToEntity<TBridgeDto>(this TBaseDto dto) where TBaseDto: IBaseDto
        {
...            
return dto;
        }


        public static TDocumentDto ToEntity<TDocumentDto>(this TDocumentDto dto, IDocumentDto currentDto) where TDocumentDto : IDocumentDto
        {
...            
return dto.ToEntity();
        }

        public static MeetingDto ToEntity(this RfiDto dto)
        {
...            
return dto.ToEntity(dto)

        }

Answer 1

Like this?

public static class Helper
{
    public static void ToEntity(this MeetingDto source)
    {
        Console.WriteLine ("MeetingDto.ToEntity");
        //Do Stuff
        (source as IDocumentDto).ToEntity();
    }

    public static void ToEntity(this ContactDto source)
    {
        Console.WriteLine ("ContactDto.ToEntity");
        //Do Stuff
        (source as IBaseDto).ToEntity();
    }

    public static void ToEntity(this IDocumentDto source)
    {
        Console.WriteLine ("IDocumentDto.ToEntity");
        //Do Stuff
        foreach (var element in source.Subscriptions)
        {
            element.ToEntity();
        }
    }

    public static void ToEntity(this IBaseDto source)
    {
        Console.WriteLine ("IBaseDto.ToEntity");
        //Do Stuff        
    }
}