Automapper expression must resolve to top-level member

Question

I am using automapper to map source and destination objects. While I map them I get the below error.

Expression must resolve to top-level member. Parameter name: lambdaExpression

I am not able resolve the issue.

My source and destination objects are:

public partial class Source
{
        private Car[] cars;

        public Car[] Cars
        {
            get { return this.cars; }
            set { this.cars = value; }
        }
}

public partial class Destination
{
        private OutputData output;

        public OutputData Output
        {            
            get {  return this.output; }
            set {  this.output= value; }
        }
}

public class OutputData
{
        private List<Cars> cars;

        public Car[] Cars
        {
            get { return this.cars; }
            set { this.cars = value; }
        }
}

I have to map Source.Cars with Destination.OutputData.Cars object. Could you please help me in this?

I tried to add the configuration, it throws error while running the configurations. My configuration looks as below Mapper.CreateMap().ForMember( dest => dest.OutputData.Cars, input => input.MapFrom(i => i.Cars)); Expression 'dest => dest.OutputData.Cars' must resolve to top-level member. Parameter name: lambdaExpression — Sandeep Reddy Pinniti, Jul 25 '12 at 06:34
This worked for me: `Mapper.CreateMap().ForMember(x => x.Cars, x => x.MapFrom(y => y.OutputData.Cars)).ReverseMap();` (also posted in an answer below) — Dominus.Vobiscum, Jan 14 '20 at 20:37
https://stackoverflow.com/questions/15554788/deep-level-mapping-using-automapper related — KushalSeth, Mar 15 '22 at 10:03

score 49 · Answer 1 · answered Oct 17 '12 at 17:25

49

You are using :

 Mapper.CreateMap<Source, Destination>()
 .ForMember( dest => dest.OutputData.Cars, 
             input => input.MapFrom(i => i.Cars));

This won't work because you are using 2 level in the dest lambda.

With Automapper, you can only map to 1 level. To fix the problem you need to use a single level :

 Mapper.CreateMap<Source, Destination>()
 .ForMember( dest => dest.OutputData, 
             input => input.MapFrom(i => new OutputData{Cars=i.Cars}));

This way, you can set your cars to the destination.

answered Oct 17 '12 at 17:25

Patrick Desjardins

136,852
88
292
341

Also used this solution for mapping between objects where the source had `string somethingKey` and `string somethingValue`, and the destination had `object something { string Key, string Value }` – st3inn Jan 10 '13 at 14:13
Greate Answer!! – Ricardo Nov 19 '16 at 15:07

score 18 · Answer 2 · answered Jun 30 '15 at 11:16

18

You can do it that way:

// First: create mapping for the subtypes
Mapper.CreateMap<Source, OutputData>();

// Then: create the main mapping
Mapper.CreateMap<Source, Destination>().
    // chose the destination-property and map the source itself
    ForMember(dest => dest.Output, x => x.MapFrom(src => src));

That's my way to do that ;-)

answered Jun 30 '15 at 11:16

Marcus.D

679
6
7

1

This is the best solution – Golan Kiviti Mar 13 '16 at 17:00
Works perfect when you want map IDataRecord to complex DTO. – ironcurtain Oct 11 '17 at 15:00
A much more elegant way, compared to the most voted answer, which could lead to some very convoluted syntax. – fhcimolin Nov 12 '21 at 17:13

score 17 · Answer 3 · answered Jul 25 '12 at 10:31

17

Define mapping between Source and OutputData.
```
Mapper.CreateMap<Source, OutputData>();
```

Update your configuration to map Destination.Output with OutputData.

Mapper.CreateMap<Source, Destination>().ForMember( dest => dest.Output, input => 
    input.MapFrom(s=>Mapper.Map<Source, OutputData>(s)));

answered Jul 25 '12 at 10:31

k0stya

4,267
32
41

I have field in the OutputData which has some default value. I don't have a mapping for this field in the source. So I didn't map it. After mapping is done, my default value is set to null value on the destination. How to avoid it setting to a null value. – Sandeep Reddy Pinniti Jul 26 '12 at 10:38

score 6 · Answer 4 · answered Jan 05 '23 at 02:35

6

ForPath works for this exact scenario.

Mapper.CreateMap<Destination, Source>().ForPath(dst => dst.OutputData.Cars, e => e.MapFrom(src => src.Cars));

answered Jan 05 '23 at 02:35

Vijayanand Settin

826
11
13

score 2 · Answer 5 · answered Jan 14 '20 at 20:35

2

This worked for me:

Mapper.CreateMap<Destination, Source>()
    .ForMember(x => x.Cars, x => x.MapFrom(y => y.OutputData.Cars))
    .ReverseMap();

answered Jan 14 '20 at 20:35

Dominus.Vobiscum

702
1
9
16

score 0 · Answer 6 · edited May 23 '17 at 11:33

The correct answer given by allrameest on this question should help: AutoMapper - Deep level mapping

This is what you need:

Mapper.CreateMap<Source, Destination>()
    .ForMember(dest => dest.OutputData, opt => opt.MapFrom(i => i));
Mapper.CreateMap<Source, OutputData>()
    .ForMember(dest => dest.Cars, opt => opt.MapFrom(i => i.Cars));

When using the mapper, use:

var destinationObj = Mapper.Map<Source, Destination>(sourceObj)

where destinationObj is an instance of Destination and sourceObj is an instance of Source.

NOTE: You should try to move away from using Mapper.CreateMap at this point, it is obsolete and will be unsupported soon.

Automapper expression must resolve to top-level member

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