[AutoMapper] Custom Type and Value converter

 .NET Core   .NET   AutoMapper 

▌Introduction

---

We can implement the following AutoMapper’s interface to customize the Type or Value converter:

1.  ITypeConverter

2.  IValueConverter

3.  IValueResolver

This article will show a few samples for how to use them.

▌Environment

---

▋AutoMapper 8.0.0

▌Implement

---

We are going to convert a MyClass1 object to MyClas2 object, that the classes are like following,

▋MyClass1

public class MyClass1 {

        public string Amount { get; set; }

        public string PayDate { get; set; }

        public string PayTime { get; set; }

    }

▋MyClass2

public class MyClass2 {

        public decimal Amount { get; set; }

        public DateTime PayOn { get; set; }

    }

▋ ITypeConverter

If the source and destination classes have too many differences to map their properties, we can implement ITypeConverter to put all the convert logic inside.

public class MyConverter : ITypeConverter<MyClass1, MyClass2>

{

    public DtoMerchantCreation Convert(MyClass1 source, MyClass2 destination, ResolutionContext context)

    {

        // Convert MyClass1 instance to MyClass2

    }

}

Usage:

var configuration = new MapperConfiguration(cfg => {

                cfg.CreateMap<MyClass1, MyClass2>().ConvertUsing<MyConverter>();

            });

▋ IValueConverter

Implement IValueConverter if the destination property’s value comes from a single property of the source.

public class AmountConverter : IValueConverter<string, decimal>

{

    public decimal Convert(string sourceMember, ResolutionContext context)

    {

         // Convert string to decimal

    }

}

Usage:

var configuration = new MapperConfiguration(cfg => {

        cfg.CreateMap<MyClass1, MyClass2>()

                    .ForMember(dest => dest.Amount, opt => opt.ConvertUsing(new AmountConverter()));

});

▋ IValueResolver

Implement IValueResolver if the destination property’s value comes from multiple properties of the source.

public class PayOnResolver : IValueResolver<MyClass1, MyClass2, DateTime>

{

    public DateTime Resolve(MyClass1 source, MyClass2 destination, DateTime destMember, ResolutionContext context)

    {

        string dateTimeStr = $"{source.PayDate} {source.PayTime}+08:00"; // e.q. "2020-03-10 08:00:00+08:00"

        return Convert.ToDateTime(dateTimeStr);

    }

}

Usage:

var configuration = new MapperConfiguration(cfg => {

        cfg.CreateMap<MyClass1, MyClass2>()

                    .ForMember(dest => dest.PayOn, opt => 

                               opt.MapFrom<PayOnResolver>())

});

Notice that if we have the other class: MyClassA, which inherits MyClass1

public class MyClassA : MyClass1 {

    }

Then it can also reuse the PayOnResolver as well. For example,

var configuration = new MapperConfiguration(cfg => {

        cfg.CreateMap<MyClassA, MyClass2>()

                    .ForMember(dest => dest.PayOn, opt => 

                               opt.MapFrom<PayOnResolver>())

});

▌Reference

---

▋https://docs.automapper.org/