Introduction

Immediate.Apis turns Immediate.Handlers handlers into ASP.NET Core minimal API endpoints at compile time.

1 min read

Immediate.Apis is a source generator that bridges Immediate.Handlers to ASP.NET Core minimal APIs. Add a [MapGet] (or [MapPost], [MapPut], …) attribute alongside [Handler], and the generator emits the app.MapGet(...) call, the request-binding attribute, the authorization conventions and an assembly-wide registration method — all at compile time, with no reflection and no runtime endpoint scanning.

Installation

dotnet add package Immediate.Apis

Prerequisites

Immediate.Handlers is required and is pulled in as a package dependency. Every endpoint is a handler first: the class must carry [Handler], or the generator emits nothing and IAPI0001 is reported as an error.
An ASP.NET Core project. The generated code calls into Microsoft.AspNetCore.Builder and Microsoft.AspNetCore.Routing, which come from the ASP.NET Core shared framework.
The package targets net8.0, net9.0 and net10.0.

A minimal example

GetUsers.cs

[Handler]
[MapGet("/users")]
public static partial class GetUsers
{
	public sealed record Query;

	private static ValueTask<IEnumerable<User>> HandleAsync(
		Query _,
		UsersService usersService,
		CancellationToken token
	)
	{
		return usersService.GetUsersAsync(token);
	}
}

Then register everything once in Program.cs:

Program.cs

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddUsersApiHandlers();

var app = builder.Build();

app.MapUsersApiEndpoints();

app.Run();

AddUsersApiHandlers comes from Immediate.Handlers; MapUsersApiEndpoints comes from Immediate.Apis. Both are named from the assembly identifier — here, a project named Users.Api.