How to use Automapper to construct object without default constructor

Question

My objects don't have a default constructor, they all require a signature of

new Entity(int recordid);

I added the following line:

Mapper.CreateMap<EntityDTO, Entity>().ConvertUsing(s => new Entity(s.RecordId));

This fixes the problem where Automapper is expecting a default constructor, however the only element that is mapped is the record id.

How do I get it to pick up on it's normal mapping? How to get all the properties of the entities to be mapped without having to manually map the properties?

Where does RecordId come from? The EntityDTO? If so, the latest version of AutoMapper found at AutoMapper.org supports mapping constructor arguments, which might help you here. — Jimmy Bogard, Aug 25 '11 at 15:46
You need to use ConstructUsing. Look at [this answer][1] for details [1]: http://stackoverflow.com/questions/2239143/automapper-how-to-map-to-constructor-parameters-instead-of-property-setters — boca, Aug 25 '11 at 15:51

score 39 · Accepted Answer · answered Aug 28 '11 at 17:07

You could use ConstructUsing instead of ConvertUsing. Here's a demo:

using System;
using AutoMapper;

public class Source
{
    public int RecordId { get; set; }
    public string Foo { get; set; }
    public string Bar { get; set; }
}

public class Target
{
    public Target(int recordid)
    {
        RecordId = recordid;
    }

    public int RecordId { get; set; }
    public string Foo { get; set; }
    public string Bar { get; set; }
}


class Program
{
    static void Main()
    {
        Mapper
            .CreateMap<Source, Target>()
            .ConstructUsing(source => new Target(source.RecordId));

        var src = new Source
        {
            RecordId = 5,
            Foo = "foo",
            Bar = "bar"
        };
        var dest = Mapper.Map<Source, Target>(src);
        Console.WriteLine(dest.RecordId);
        Console.WriteLine(dest.Foo);
        Console.WriteLine(dest.Bar);
    }
}

The ConvertUsing gives more flexibility when it comes to map from the viewmodel to model. Is there any way that I could use ConstructUsing with ConvertUsing? I would like to just map a few properties when mapping from viewModel to model with a constructor but when mapping from model to view model all properties should be mapped. — akd, Jan 15 '17 at 03:29
Is there a way to make it more generic? Usecase: Convert from parent to child and whatever fields doent exist in parent, pass them as null in child — user1324887, Aug 28 '20 at 21:58

score 8 · Answer 2 · answered Aug 28 '11 at 17:04

8

Try

Mapper.CreateMap<EntityDTO, Entity>().ConstructUsing(s => new Entity(s.RecordId));

answered Aug 28 '11 at 17:04

CassOnMars

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How to use Automapper to construct object without default constructor

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