Use Automapper for mapping big domain models to database objects

Question

I would like to use Automapper to map my model objects to database objects. Let say database object is over 30 fields and I want map 10 out of 20 properties from my model. To make it more complex I need to map different properties when I update record than when I insert new record to database.

The solution I'm using is to create 2 generic classes Insert and Update and mapping profile that specifies both mappings.

The example below:

public abstract class SyncMappingWrapper<TFrom> where TFrom : class
{
    protected SyncMappingWrapper(TFrom model)
    {
        Model = model;
    }

    public TFrom Model { get; private set; }
}

public class Update<TFrom> : SyncMappingWrapper<TFrom> where TFrom : class
{
    public Update(TFrom model)
        : base(model)
    {
    }
}

public class Insert<TFrom> : SyncMappingWrapper<TFrom> where TFrom : class
{
    public Insert(TFrom model)
        : base(model)
    {
    }
}

The mapping, however, is getting nasty as cyclomatic complexity goes in to the sky (over 50) as I need to define Ignore() for all properties I don't map:

CreateMap<Update<OracleModel>, LiveModel>()
            .ForMember(des => des.ApprovedBy, opt => opt.Ignore())
            .ForMember(des => des.ApprovedDate, opt => opt.Ignore())
            ...
            .ForMember(des => des.UNSPSC, opt => opt.Ignore())
            .ForMember(des => des.BaseUnit, opt => opt.MapFrom(src => src.Model.UOM.BaseUOM.PerSalesUnit))
            .ForMember(des => des.BaseUOM, opt => opt.MapFrom(src => src.Model.UOM.BaseUOM.UnitOfMeasure.Code))
            .ForMember(des => des.SalesUnit, opt => opt.MapFrom(src => src.Model.UOM.SalesUOM.PerSalesUnit))
            .ForMember(des => des.SalesUOM, opt => opt.MapFrom(src => src.Model.UOM.SalesUOM.UnitOfMeasure.Code))
            .ForMember(des => des.OrderUnit, opt => opt.MapFrom(src => src.Model.UOM.OrderUOM.PerSalesUnit))
            .ForMember(des => des.OrderUOM, opt => opt.MapFrom(src => src.Model.UOM.OrderUOM.UnitOfMeasure.Code))
            .ForMember(des => des.SalesPrice, opt => opt.MapFrom(src => src.Model.Price.Value))
            .ForMember(des => des.Alternate, opt => opt.Ignore())
            .ForMember(des => des.ManufacturerID, opt => opt.Ignore())
            .ForMember(des => des.ProductCode, opt => opt.MapFrom(src => src.Model.ProductCode))
            .ForMember(des => des.ProductName, opt => opt.MapFrom(src => src.Model.ProductName))
            .ForMember(des => des.ProductHTML, opt => opt.Ignore())
            .ForMember(des => des.Version, opt => opt.Ignore())
            ...
            .ForMember(des => des.UnitsOfMeasure2, opt => opt.Ignore())
            .ForMember(des => des.Manufacturer, opt => opt.Ignore());

I've solved the problem for inserting new record by creating new object:

CreateMap<Insert<OracleModel>, LiveModel>()
            .ConstructUsing(x => new LiveModel
                {
                    BaseUnit = x.Model.UOM.BaseUOM.PerSalesUnit,
                    BaseUOM = x.Model.UOM.BaseUOM.UnitOfMeasure.Code,
                    SalesUnit = x.Model.UOM.SalesUOM.PerSalesUnit,
                    SalesUOM = x.Model.UOM.SalesUOM.UnitOfMeasure.Code,
                    OrderUnit = x.Model.UOM.OrderUOM.PerSalesUnit,
                    OrderUOM = x.Model.UOM.OrderUOM.UnitOfMeasure.Code,
                    SalesPrice = x.Model.Price.Value,
                    LeadTime = x.Model.LeadTime,
                    ProductCode = x.Model.ProductCode,
                    ProductName = x.Model.ProductName,
                    SupplierCode = x.Model.SupplierCode,
                    Weight = x.Model.Weight
                })
            .ForAllMembers(xc => xc.Ignore());

But it doesn't work for updates where I want to map properties to an existing object and not new instance:

        Mapper.Map(update, existingRecord);

I would prefer to avoid DynamicMap() to keep full control over the mapping (so I will not map a random property by mistake). My target is to sort out cyclomatic complexity problem. Please do not suggest ValueInjecter or any other methods. I'm looking for solution within AutoMapper.

Answer 1

It's five years later, but here's a suggestion to reduce this mapping complexity problem. You can create an extension that will help you ignore all members at first:

public static class AutoMapperExtension {
    public static IMappingExpression<TSource, TDest> IgnoreAllMembers<TSource, TDest>(this IMappingExpression<TSource, TDest> expression) {
        expression.ForAllMembers(opt => opt.Ignore());
        return expression;
    }
}

Then you use it to define only the mappings you want to perform:

Mapper.CreateMap<Insert<OracleModel>, LiveModel>()
      .IgnoreAllMembers()
      .ForMember(d => d.BaseUnit, o => o.MapFrom(s => s.Model.UOM.BaseUOM.PerSalesUnit))
      /* Mapping for other members here. */;