Mapster - The Mapper of Your Domain

Writing mapping methods is a machine job. Do not waste your time, let Mapster do it.

NuGet Sources

NuGet Packages

Package	Stable	Pre-release
Mapster
Mapster.Core
Mapster.DependencyInjection
Mapster.EFCore
Mapster.EF6
Mapster.JsonNet
Mapster.Immutable
Mapster.Diagnostics
ExpressionDebugger

DotNet Tools

Tool	Stable	Pre-release
Mapster.Tool

Installation

Install Mapster with the NuGet CLI:

Install-Package Mapster

Or use the .NET core CLI to install Mapster:

dotnet add package Mapster --project <PROJECT_NAME>

Basic usage

Mapping to a new object

Mapster creates the destination object and maps values to it.

var destObject = sourceObject.Adapt<Destination>();

Mapping to an existing object

You create the object, Mapster maps to the object.

sourceObject.Adapt(destObject);

Use Mapster with Dependency Injection

You can get your IMapper instance via dependency injection, so you do not have to change code, when migrating to mapster from automapper!

Just add Mapster to service collection:

services.AddMapster();

And use it with DI in your Project:

public class Test
{
    public Test(IMapper mapper)
    {
        var sourceObject = mapper.Adapt<Destination>();
    }
}

Queryable Extensions

Mapster also provides extensions to map queryables.

using (MyDbContext context = new MyDbContext())
{
    // Build a Select Expression from DTO
    var destinations = context.Sources.ProjectToType<Destination>().ToList();

    // Versus creating by hand:
    var destinations = context.Sources.Select(c => new Destination {
        Id = c.Id,
        Name = c.Name,
        Surname = c.Surname,
        ....
    })
    .ToList();
}

Generating models & mappers

No need to write your own DTO classes. Mapster provides Mapster.Tool to help you generating models. And if you would like to have explicit mapping, Mapster also generates mapper class for you.

[AdaptTo("[name]Dto"), GenerateMapper]
public class Student {
    ...
}

Then Mapster will generate for you:

public class StudentDto {
    ...
}
public static class StudentMapper {
    public static StudentDto AdaptToDto(this Student poco) { ... }
    public static StudentDto AdaptTo(this Student poco, StudentDto dto) { ... }
    public static Expression<Func<Student, StudentDto>> ProjectToDto => ...
}

What's new

• Fluent API for code generation
• Automatically generate mapping code on build
• Define setting to nested mapping
• ISet, IDictionary, IReadOnlyDictionary support
• EmptyCollectionIfNull, CreateNewIfNull DestinationTransform
• Several fixes
• New plugins
  • Immutable collection support

Why Mapster?

Performance & Memory efficient

Mapster was designed to be efficient on both speed and memory. The repository includes a benchmark project in src/Benchmark that compares the local Mapster build, its compiler variants, and other modern mapping libraries like AutoMapper, Mapperly, and Facet.

• Roslyn Compiler
• FEC
• Code generation
• Facet
• Mapperly

The snapshot below shows the FlatTypes scenario (Person -> PersonDTO), a best-case DTO with simple property-to-property mapping and no nested objects or collections.

Method	MapOperations	Mean	StdDev	Error	Ns/Map	Ratio	Gen0	Allocated	Alloc Ratio	Bytes/Map
Mapster 10.0.8	1000000	6.849 ms	0.6851 ms	1.0358 ms	6.849	1.01	4781	76.29 MB	1.00	80
Mapster 10.0.8 (Roslyn)	1000000	6.579 ms	0.2782 ms	0.4206 ms	6.579	0.97	4781	76.29 MB	1.00	80
Mapster 10.0.8 (FEC)	1000000	6.549 ms	0.9130 ms	1.3803 ms	6.549	0.97	4781	76.29 MB	1.00	80
Mapster 10.0.8 (Codegen)	1000000	5.868 ms	0.3266 ms	0.5488 ms	5.868	0.86	4781	76.29 MB	1.00	80
AutoMapper 14.0.0	1000000	29.645 ms	0.8963 ms	1.5062 ms	29.645	4.37	4750	76.29 MB	1.00	80
Facet 6.5.5	1000000	7.801 ms	1.0231 ms	1.5467 ms	7.801	1.15	8601	137.33 MB	1.80	144
Facet 6.5.5 (Compiled Projection)	1000000	5.508 ms	0.7064 ms	1.0679 ms	5.508	0.81	4781	76.29 MB	1.00	80
Mapperly 4.3.1	1000000	6.521 ms	0.8369 ms	1.2652 ms	6.521	0.96	4781	76.29 MB	1.00	80

Step into debugging

Step-into debugging lets you debug your mapping and inspect values just like your code.

Code Generation

Code generation allows you to

• Validate mapping at compile time
• Getting raw performance
• Seeing your mapping code & debugging
• Finding usage of your models' properties

There are currently two tools which you can choose based on your preferences.

• Mapster.Tool NEW!
• TextTemplate

Change logs

https://github.com/MapsterMapper/Mapster/releases

Usage Guides with Translations

• English
• 中文文档 (sp thx to @staneee)

Acknowledgements

JetBrains kindly provides Mapster with a free open-source licence for their Resharper and Rider.

• Resharper makes Visual Studio a much better IDE
• Rider is fast & powerful cross platform .NET IDE