Injecting into an AutoMapper TypeConverter using AutoFac in .NET Framework 4.8

In my current project, we are still using .NET Framework for several applications. At one point, I needed to use a custom TypeConverter from AutoMapper during the mapping process. However, I wanted to inject an object into the TypeConverter using Autofac, and it wasn't immediately clear how to achieve this. While searching the internet, I found plenty of information for .NET (Core), but for .NET Framework, only a few pieces of the puzzle were provided.

After some experimentation, I managed to piece everything together. Below is a comprehensive code sample that demonstrates the solution. You can easily run this in Visual Studio 2022—simply create a new Console Application targeting .NET Framework, paste the sample code, and you're all set to run and learn!

using Autofac; // 7.1.0 
using AutoMapper; // 10.0.0 
using System; // .NET Framework 4.8 
  
namespace ConsoleApp7 
{ 
    // a person-class, which we will map from 
    public class Person 
    { 
        public string Name { get; set; } 
        public DateTime DateOfBirth { get; set; } 
    } 
  
    // another person-class, which we will map to 
    public class PersonDto 
    { 
        public string Name { get; set; } 
        public DateTime DateOfBirth { get; set; } 
    } 
  
    // a simple interface for the object that we want to inject 
    public interface IStringMaker 
    { 
        string Create(); 
    } 
  
    // a simple implementation to create a simple string 
    public class StringMaker : IStringMaker 
    { 
        public string Create() 
        { 
            return "abc123"; 
        } 
    } 
  
    // A custom AutoMapper Type Converter. 
    public class MyTypeConverter : ITypeConverter<Person, PersonDto> 
    { 
        private readonly IStringMaker _stringMaker; 
  
        // The constructor gets injected by an interface 
        public MyTypeConverter(IStringMaker stringMaker) 
        { 
            _stringMaker = stringMaker; 
        } 
  
        public PersonDto Convert(Person source, PersonDto destination, ResolutionContext context) 
        { 
            return new PersonDto 
            { 
                Name = $"converted {source.Name} {_stringMaker.Create()}", // note that the injected object gets used here 
                DateOfBirth = source.DateOfBirth 
            }; 
        } 
    } 
  
    internal class Program 
    { 
        static void Main(string[] args) 
        { 
            // SETUP starts here 
            // AutoFac 
            var builder = new ContainerBuilder(); 
  
            // register both the object to inject and the type converter 
            builder.RegisterType<StringMaker>() 
                .As<IStringMaker>(); 
            builder.RegisterType<MyTypeConverter>(); 
  
            // register the AutoMapper mappingconfiguration 
            var mapperConfig = new MapperConfiguration(cfg => cfg.CreateMap<Person, PersonDto>().ConvertUsing<MyTypeConverter>()); 
            builder.Register(c => mapperConfig); 
  
            // register the mapper itself 
            builder.Register(c => { 
                var context = c.Resolve<IComponentContext>(); 
                var config = context.Resolve<MapperConfiguration>(); 
                return config.CreateMapper(context.Resolve); 
            }).As<IMapper>(); 
  
            var container = builder.Build(); 
            // SETUP ends here 
  
  
            // retrieve the mapper from AutoFac 
            var mapper = container.Resolve<IMapper>(); 
  
            var person = new Person { Name = "John", DateOfBirth = new DateTime(1990, 12, 6) }; 
  
            var dto = mapper.Map<Person, PersonDto>(person); 
            // dto.Name will be "converted John abc123" at this point 
  
            Console.ReadLine(); 
        } 
    } 
}