README.md

GeneratedMapper

Compile-time object-to-object mapper generator which generates extension methods for each of the mappings.

Install-Package GeneratedMapper

(Sometimes VS2019 needs to be restarted after adding the package)

Bad informercial

How often do you have a certain model like..

public class SourceDTO
{
    public string Name { get; set; }

    public string SomeProp { get; set; }
}

..which must be mapped to a model like..

public class DestinationViewModel
{
    public string Name { get; set; }

    public string SomeProp { get; set; }
}

..but you don't want the runtime surpises and performance hits of an AutoMapper, ExpressionMapper, or any other mapper?

Introducing GeneratedMapper, the compile-time object-to-object mapper that generates mappings at compile-time! Just slap on some attributes, and have your computer work for YOU!

This extension method..

public static partial class SourceDTOMapToExtensions
{
    public static DestinationViewModel MapToDestination(this SourceDTO self)
    {
        if (self is null)
        {
            throw new ArgumentNullException(nameof(self));
        }
            
        var target = new DestinationViewModel
        {
            Name = self.Name,
            SomeProp = self.SomeProp
        };
            
        return target;
    }
}

..can be yours if pick up your phone now and add the following attribute to your class:

[MapTo(typeof(DestinationViewModel))]
public class SourceDTO
{
    public string Name { get; set; }

    public string SomeProp { get; set; }
}

Don't delay, generate your object-to-object mappers at compile-time today!

Features

Mapping

• Property to property mapping (Title -> target.Title = source.Title).
• Property to property mapping with different names ([MapWith("TheTitle")] Title -> target.TheTitle = source.Title).
• Property to property mapping using (extension) method ([MapWith("TheTitle", "Substring")] Title -> target.TheTitle = source.Title.Substring(startIndex)).
• Property to property mapping using resolver ([MapWith("TheTitle", typeof(Resolver))] Title -> target.TheTitle = resolver.Resolve(source.Title)).
• Enumeration mapping (Codes -> target.Codes = (source.Codes ?? Enumerable.Empty<string>()).ToArray()).
• Dictionary mapping (Definitions -> target.Definitions = (source.Codes ?? Enumerable.Empty<KeyValuePair<string, string>>()).ToDictionary(x => x.Key, x => x.Value)).
• Async mapping using [MapAsyncWith("Property", "AsyncMethodAsync")], [MapAsyncWith("Property", "AsyncExtensionMethodAsync")], or [MapAsyncWith("Property", typeof(AsyncResolver))].
• Simple nested property mapping ([MapWith("Sys.Id")]Id -> target.Id = source.Sys?.Id)

Configuration

Use [assembly: MapperGeneratorConfiguration()] to configure the mapper, like always including certain namespaces if the mapper fails to recognize them, or configure what exceptions should be thrown when the mapper encounters null.

• ThrowWhenNotNullablePropertyIsNull: Configures whether the mapper should throw when a non-nullable property is null.
• ThrowWhenNotNullableElementIsNull: Configures whether the mapper should throw when a non-nullable element in a collection is null.
• NamespacesToInclude: Configures extra namespaces to include in mappers when they prove to be too hard to be recognized by the mapper.
• GenerateEnumerableMethods: Configures if for every X.MapToY() also a IEnumerable.MapToYs() must be generated.
• GenerateExpressions: Configures if for every mapper, the mapping should also be available as Expression<Func<X, Y>> for use in APIs which require expressions (like EF or Mongo).
• GenerateInjectableMappers: Generates a IMapper<From, To> for each extension method, which can be added to the DI container using services.AddMappers().

More information

Please review the Example project to find more examples. The GeneratedMapper.Tests project contains a lot of unit tests which also show what is possible.