FBC.Mediator

FBC.Mediator is a lightweight, high-performance Mediator pattern implementation for .NET projects.
It provides command/query dispatching, request handler caching, and endpoint registration for ASP.NET Core.

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Features

• IMediator for type-safe request/response and void requests
• Supports IRequestHandler<TRequest, TResponse> and IRequestHandler<TRequest>
• Request handler caching for performance
• Easy integration with ASP.NET Core Minimal APIs
• Compatible with Swagger/OpenAPI
• Auto-registration of handlers and endpoints

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Installation

// In Startup.cs or Program.cs
builder.Services.AddMediator(typeof(Program).Assembly);
...
var app = builder.Build();
...
app.UseMediatorEndpoints();
...

You can pass multiple assemblies if your handlers or endpoints are spread across projects.

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Usage

Request & Response

Define a request:

public sealed class CreateItem
{
    public record Command(string Name) : IRequest<long>;

    internal sealed class Handler(ILogger<Handler> logger) : IRequestHandler<Command, long>
    {
        public async Task<long> Handle(Command request, CancellationToken token = default)
        {
            logger.LogInformation("Creating item with Name: {ItemName}", request.Name);
            // Perform your logic here
            await Task.Delay(100, token); // simulated async operation
            return new Random().Next(1, 1000); // example ID
        }
    }
}

Define an endpoint:

public sealed class CreateItemEndPoint : IEndpoint
{
    public void AddRoutes(IEndpointRouteBuilder app)
    {
        app.MapPost("/items/create", async (CreateItem.Command command, IMediator mediator, CancellationToken token) =>
        {
            var itemId = await mediator.Send(command, token);
            return Results.Ok(itemId);
        })
        .WithTags("Items")
        .WithName("CreateItem")
        .WithSummary("Creates a new item.")
        .WithDescription("Creates a new item and returns the ID of the created item.")
        .Produces<long>(StatusCodes.Status200OK)
        .Produces(StatusCodes.Status400BadRequest)
        .Produces(StatusCodes.Status500InternalServerError);
    }
}

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Void Request

Use a void request:

public sealed class VoidTest
{
    public record Command() : IRequest;

    internal sealed class Handler(ILogger<Handler> logger) : IRequestHandler<Command>
    {
        public async Task Handle(Command request, CancellationToken token = default)
        {
            logger.LogInformation("Handling void command");
            await Task.CompletedTask;
        }
    }
}

Endpoint for void request:

public sealed class VoidTestEndPoint : IEndpoint
{
    public void AddRoutes(IEndpointRouteBuilder app)
    {
        app.MapPost("/voidtest", async (VoidTest.Command command, IMediator mediator, CancellationToken token) =>
        {
            await mediator.Send(command, token);
            return Results.Ok();
        })
        .WithTags("Test")
        .WithName("VoidTest")
        .WithSummary("Tests void command.")
        .WithDescription("Sends a void command and returns OK.")
        .Produces(StatusCodes.Status200OK)
        .Produces(StatusCodes.Status400BadRequest)
        .Produces(StatusCodes.Status500InternalServerError);
    }
}

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DI and Endpoint Integration

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddMediator(typeof(Program).Assembly);

var app = builder.Build();

app.UseMediatorEndpoints();

• AddMediator automatically registers all handlers and endpoints.
• UseMediatorEndpoints maps all IEndpoint implementations to the route builder.

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Swagger/OpenAPI Support

FBC.Mediator includes a safe schema ID selector for Swagger, ensuring nested classes or records display correctly.

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Summary

• Type-safe, generic, and high-performance mediator
• Minimal API-friendly
• Handler caching for fast request dispatch
• Supports void and generic requests
• Compatible with Swagger/OpenAPI

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Recommended Usage

1. Use IRequest<TResponse> for commands and queries.
2. Use IRequest for void operations.
3. Define endpoints using IEndpoint.
4. Register the mediator using AddMediator.
5. Map endpoints using UseMediatorEndpoints.