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DeeDee is a high performance, low memory library used for dispatching and handing of in-process requests. It allows you to create a pipeline of actions that can be performed on these requests and supports short circuiting.

Requirements

As this library uses Source Generators, it targets .NET 6

Getting started

Install package from Nuget Install-Package DeeDee

If your application already uses Microsoft.Extensions.DependencyInjection, simply call services.AddDispatcher().

If you use some other DI framework, you will have to make sure to wire up ServiceProvider delegate to represent your container.

For example:

services.AddSingleton<DeeDee.Models.ServiceProvider>(ctx => ctx.GetService);

as well as registering the IDispatcher in your container.

service.AddSingleton<IDispatcher, Dispatcher>()

How To

There are 2 different types of requests that are supported.

• IRequest that will return no data. This maps to void for sync or Task for async calls.
• IRequest<TResponse> that returns a TResponse. This maps to TResponse for sync calls and Task<TResponse> for async calls.

Examples

Send a request that will return nothing

public class GetARequest : IRequest
{

}

public class HandlerA : IPipelineActionAsync<GetARequest>
{
    public Task InvokeAsync(GetARequest request, PipelineContext context, NextAsync next, CancellationToken cancellationToken = default)
    {
        return Task.CompletedTask;
    }
}

await _dispatcher.SendAsync(new GetARequest());

Send a request that will return an int

public class GetBRequest : IRequest<int>
{

}

public class HandlerB : IPipelineActionAsync<GetBRequest, int>
{
    public Task<int> InvokeAsync(GetBRequest request, PipelineContext<int> context, NextAsync<int> next, CancellationToken cancellationToken = default)
    {
        return Task.FromResult(42);
    }
}

var result = await dispatcher.SendAsync(new GetBRequest());

Due to the dynamic code generation, the SendAsync method will now have 2 overloads, one for each request that exists with full IDE visibility.

You can build up a pipeline of these handlers too

public class GetBRequest : IRequest<int>
{
    public bool Toggle {get;}

    public GetBRequest(bool toggle)
    {
        Toggle = toggle;
    }
}

[Step(1)]
public class ValidateHandlerB : IPipelineActionAsync<GetBRequest, int>
{
    public Task<int> InvokeAsync(GetBRequest request, PipelineContext<int> context, NextAsync<int> next, CancellationToken cancellationToken = default)
    {
        //if not toggled, then short circuit rest of the pipeline
        if(!request.Toggle)
            return Task.FromResult(42);
        //you can store data that will be available to all handlers in the pipeline
        context.AddItem("SomeKey", "SomeValue");
        //call the next pipeline
        return next(request, context, cancellationToken);
    }
}


[Step(2)]
public class HandlerB : IPipelineActionAsync<GetBRequest, int>
{
    public Task<int> InvokeAsync(GetBRequest request, PipelineContext<int> context, NextAsync<int> next, CancellationToken cancellationToken = default)
    {
        //retrieve data from bag
        if(!context.TryGetValue("SomeKey", out var value))
           throw new Exception();
        //either set the Result if you have more actions in your pipeline
        context.Result = 42;
        return next(request, context, cancellationToken);
   
       //OR directly return the result
       // return Task.FromResult(42);

    }
}

var result = await dispatcher.SendAsync(new GetBRequest());

The Step() attribute determines the order of your handlers in the pipeline;

The PipelineContext uses a custom FrugalDictionary that will only allocate when it reaches 11 or more items.

The sync version implements IPipelineAction

Performance

Due to the dynamic code generation, all types are known during compile time. This avoids reflection and constant ConcurrentDictionary lookups.

Below is the benchmarks performed against the highly popular Mediatr library.

|  Method |      Mean |     Error |    StdDev | Ratio | RatioSD |  Gen 0 | Gen 1 | Gen 2 | Allocated |
|-------- |----------:|----------:|----------:|------:|--------:|-------:|------:|------:|----------:|
|  DeeDee |  60.89 ns |  2.324 ns |  6.742 ns |  1.00 |    0.00 | 0.0057 |     - |     - |      24 B |
| Mediatr | 337.21 ns | 10.659 ns | 30.583 ns |  5.59 |    0.80 | 0.1106 |     - |     - |     464 B |

DeeDee is almost 6x faster and allocates almost 20x less.