Question

I am trying to separate my MVC3 project into a proper DAL/Domain/ViewModel architecture, but I’m running into a problem with AutoMapper and mapping calculated fields from my domain to my view model.

Here’s an example of what I’m trying to do:

Interface

public interface IRequirement
{
    int Id { get; set; }
    ... bunch of others
    public decimal PlanOct { get; set; }
    public decimal PlanNov { get; set; }
    public decimal PlanDec { get; set; }
    ... and so on
    decimal PlanQ1 { get; }
    ... etc
    decimal PlanYear { get; }
    ... repeat for ActualOct, ActualNov ... ActualQ1 ... ActualYear...
}

Domain Model

public class Requirement : IRequirement
{
    public int Id { get; set; }
    ... bunch of others
    public decimal PlanOct { get; set; }
    public decimal PlanNov { get; set; }
    public decimal PlanDec { get; set; }
    ... and so on
    public decimal PlanQ1 { get { return PlanOct + PlanNov + PlanDec; } }
    ... etc
    public decimal PlanYear { get { return PlanQ1 + PlanQ2 + PlanQ3 + PlanQ4; } }
    ... repeat for ActualOct, ActualNov ... ActualQ1 ... ActualYear...
}

There are also VarianceX properties, i.e. VarianceOct which is calculated as (PlanOct – ActualOct), etc.

My view model looks almost exactly the same, except instead of calculated fields it has the default getter/setter syntax, for example:

public decimal PlanQ1 { get; set; }

My AutoMapper config in Global.asax looks like this:

Mapper.CreateMap<Domain.Abstract.IRequirement, Models.Requirement.Details>();

This works fine on all properties except the calculated ones. None of my calculated fields (i.e. *Q1, *Q2, *Q3, *Q4, *Year, and all the Variance* fields) are actually mapped — they all show up with the default value of 0.00.

I’m pretty stumped on this, and I’m also a novice at this and AutoMapper, so maybe I missed something. My intuition is that since the property signatures aren’t identical (i.e. the domain object has only a non-default getter and no setter, while the view model has default getter and setter) then AutoMapper isn’t picking it up. But I also did this:

Mapper.CreateMap<Domain.Abstract.IRequirement, Models.Requirement.Details>()
            .ForMember(dest => dest.PlanQ1, opt => opt.MapFrom(src => src.PlanQ1);

And it still resolved to 0. I confirmed this in the debugger as well.

What am I doing wrong?

Thanks in advance.

EDIT 1

After following Wal’s advice I ran the test and it worked, so I began working backwards one step at a time, first pasting in the Field1/Field2/Field3 parts into the interface/domain/view model classes and verifying it worked in my controller, then changing one thing at a time. What I found is that, since I am dealing with decimal types, if I hard-code in integer or double values then I get zero, but if I cast to a decimal or use a decimal literal then it works. But only if I manually set them, not if I pull the values from the database.

In other words, this works (i.e. PlanQ1 = 6):

var D = new Requirement { PlanOct = (decimal) 1.0, PlanNov = (decimal) 2.0, PlanDec = (decimal) 3.0 };
var V = Mapper.Map<IRequirement, Details>(D);

And this works:

var D = new Requirement { PlanOct = 1M, PlanNov = 2M, PlanDec = 3M };
var V = Mapper.Map<IRequirement, Details>(D);

But this does not (pulling a single domain object from a repository object, that in turn pulls from SQL Server using Entity Framework):

var D = requirementRepository.Requirement(5);
var V = Mapper.Map<IRequirement, Details>(D);

With the above all I get is 0 for PlanQ1 and PlanYear. I verified that PlanOct = 1, PlanNov = 2, and PlanDec = 3 in the domain object (D). I also verified that the type in all objects, including the EF generated object, is decimal, and the SQL Server type is decimal. I even tried mapping to a created view model, just to rule that out, and I still get 0 for PlanQ1 and PlanYear:

var D = requirementRepository.Requirement(5);
var V = new Details();
Mapper.Map<IRequirement, Details>(D, V);

Answer 1

Just realized this was left unanswered so I wanted to close it out. Technically it is unanswered because I couldn’t get Automapper to play nice in this scenario for some reason. What I wound up doing is going back and creating a couple of mapping methods inside my repository, one to map a single instance of the DAL object to the IRequirement object, and one to map a collection. Then in the repository instead of calling Mapper.Map I just call my custom mapping methods and it works perfectly.

I still don’t understand why this doesn’t work, but I’ve run into a few other classes where Automapper just throws up and I have to manually map at least one or two fields, though Automapper does take care of the rest in those cases.

I’m sure there’s something about it I just don’t see yet. But in any case, falling back to partial or fully manual mapping was my workaround.