Immediate.Handlers

Creating behaviors

Pipeline behaviors allow you to inject your own logic around the handling of requests, which lets you build a pipeline to address common cross-cutting concerns such as logging, validation etc. In fact, Immediate.Validations performs its validation of your queries and commands by using a behavior.

You can think of behaviors as akin to filters known from ASP.NET Core.

# Creating a behavior

Behaviors can be created by implementing the Immediate.Handlers.Shared.Behaviors<,> class, as so:

        public sealed class LoggingBehavior<TRequest, TResponse>(ILogger<LoggingBehavior<TRequest, TResponse>> logger)
	: Behavior<TRequest, TResponse>
{
	public override async ValueTask<TResponse> HandleAsync(TRequest request, CancellationToken cancellationToken)
	{
		logger.LogInformation("LoggingBehavior.Enter");
		var response = await Next(request, cancellationToken);
		logger.LogInformation("LoggingBehavior.Exit");
		return response;
	}
}

      

This can be registered assembly-wide using:

        [assembly: Behaviors(
	typeof(LoggingBehavior<,>)
)]

      

or on an individual handler using:

        [Handler]
[Behavior(
	typeof(LoggingBehavior<,>)
)]
public static class GetUsersQuery
{
	// ..
}

      

Once added to the pipeline, the behavior will be called as part of the pipeline to handle a request.

# Behavior Constraints

A constraint can be added to a behavior by using:

        public sealed class LoggingBehavior<TRequest, TResponse>
	: Behavior<TRequest, TResponse>
	where TRequest : IRequestConstraint
	where TResponse : IResponseConstraint

      

When a pipeline is generated, all potential behaviors are evaluated against the request and response types, and if either type does not match a given constraint, the behavior is not added to the generated pipeline.

# Registering with IServiceCollection

Immediate.Handlers supports Microsoft.Extensions.DependencyInjection.Abstractions directly. To register behaviors with DI, simply add the following to your Program.cs:

        services.AddBehaviors();

      

This registers all behaviors referenced in any [Behaviors] attribute.