MediatR.Extensions.AttributedBehaviors

MediatR extension adding ability to specify pipeline behaviors using attributes on command class. Leverages Microsoft.Extensions.DependencyInjection as a DI container.

Ever found yourself confused when looking for behaviors that are attached to the pipeline you are about to debug? Keeping all behaviors specified within the command class makes it really clear.

// Instead of this
 services.AddScoped<IPipelineBehavior<MyRequest, MyReturnType>, MyFirstPipelineBehavior<MyRequest, MyReturnType>>()
         .AddScoped<IPipelineBehavior<MyRequest, MyReturnType>, MySecondPipelineBehavior>();

// You write this
[MediatRBehavior(typeof(MyFirstPipelineBehavior<MyRequest, MyReturnType>))]
[MediatRBehavior(typeof(MySecondPipelineBehavior))]
public class MyRequest : IRequest<MyReturnType> { }

You immediately see all the behaviors your request passes through in order as they are specified. No need to search in your code base for behaviors installation to see what behaviors are used.

Install

Install with Package Manager Console

Install-Package MediatR.Extensions.AttributedBehaviors

Install with .NET CLI

dotnet add package MediatR.Extensions.AttributedBehaviors

How to use

Setup - Add configuration in startup.cs

public void ConfigureServices(IServiceCollection services)
{   
    var executingAssembly = Assembly.GetExecutingAssembly()
    // Add MediatR
    services.AddMediatR(executingAssembly);

    // optionally register open generics universal behaviors (e.g. logging)
    // before registering attributed behaviors
    services.AddScoped(typeof(IPipelineBehavior<,>), typeof(LoggingPipelineBehavior<,>));

    //Add Attributed Behaviors
    services.AddMediatRAttributeBehaviors(executingAssembly);
    
    //Add other stuff
    ...
}

Use

You no longer need to register your behaviors in service collection. You can keep them clearly visible right where they are used

// no longer needed
 services.AddScoped<IPipelineBehavior<GetValidEventUrlRequest, ValidEventUrl>, ResolveEventIdByPublicIdPipelineBehavior<GetValidEventUrlRequest, ValidEventUrl>>()
         .AddScoped<IPipelineBehavior<GetValidEventUrlRequest, ValidEventUrl>, CheckEventDisabledPipelineBehavior<GetValidEventUrlRequest, ValidEventUrl>>();



// instead you can just simply specify them like this
[MediatRBehavior(typeof(ResolveEventIdByPublicIdPipelineBehavior<GetValidEventUrlRequest, ValidEventUrl>))]
[MediatRBehavior(typeof(CheckEventDisabledPipelineBehavior<GetValidEventUrlRequest, ValidEventUrl>))]
public class GetValidEventUrlRequest : IRequest<ValidEventUrl>
{
    public string PublicId { get; set; }
    public int EventId { get; set; }
}

Custom behavior life-cycle

By default, Scoped lifetime is used. You can use your own lifetime as desired

// singleton behavior
[MediatRBehavior(typeof(MySingletonPipelineBehavior<MyQuery>), serviceLifetime: ServiceLifetime.Singleton)]
public class MyQuery : IRequest

Custom behavior ordering

By default, behaviors are ordered based on the line number - as they are specified top-to-bottom. If you ever need to specify your custom ordering, you can.

// override default top->bottom ordering
[MediatRBehavior(typeof(SecondPipelineBehavior<MyQuery>), order: 2)]
[MediatRBehavior(typeof(FirstPipelineBehavior<MyQuery>), order: 1)]
public class MyQuery : IRequest

Changelog

3.0.0

• Updated MediatR dependency to 12.x
• Dropped direct reference to Microsoft.Extensions.DependencyInjection.Abstractions
• Updated tests based on breaking changes from MediatR 12.x

2.0.0

• Updated MediatR dependency to 10.x
• Dropped support for netstandard2.0

1.0.2

• Fixed Service collection extensions
• Added unit tests

1.0.1

• Matched dependencies versions with MediatR

1.0.0

• Initial version