.NET 6 Minimal API

.NET 6 comes with a new template for C# WebAPIs which is much more minimal. This exercise walks through setting up some endpoints in that template without using controllers.

Prerequisites:

.NET 6.0

Visual Studio Code

Loose Agenda:

Set up APIs in the .NET 6 WebAPI template without controllers

Step by Step

Setup Playground

Create a directory for today's exercise and navigate to it in a terminal instance.

Run dotnet new webapi then open the directory in Visual Studio Code.

Clean up Controllers

Delete the Controllers directory.

Delete WeatherForecast.cs.

Open Program.cs

Replace builder.Services.AddControllers(); with builder.Services.AddEndpointsApiExplorer();

Move these lines out of the if-block

app.UseSwagger();
app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "net_6_minimal_api v1"));

Remove app.UseAuthorization(); and app.MapControllers();

Add a GET endpoint

Just above app.Run(); let's add the following code:

app.MapGet("/example", () => {
    return "This is an example of a GET endpoint";
});

Run the code via dotnet run in the terminal instance and navigate to localhost:5001/swagger

Dependency Injection

To demonstrate dependency injection, let's create a class which we can inject and call for a result.

Create a new file named DemoService.cs with the following code:

public class DemoService
{
    public string NeedlesslyConsumeResources() {
        return "Non-Zero Memory Consumption";
    }
}

Back in Program.cs just below var builder = WebApplication.CreateBuilder(args); add the following line

builder.Services.AddScoped<DemoService>();

Now let's add another GET endpoint with the following code:

app.MapGet("/demo", (DemoService _service) => {
    return _service.NeedlesslyConsumeResources();
});

Note that dependency injection is occuring naturally through the delegate parameter.

Run the code via dotnet run in the terminal instance and navigate to localhost:5001/swagger

ActionResults

Let's end by demonstrating ActionResults as a return type in minimal APIs

One more GET endpoint, but this one will be tempermental.

app.MapGet("/actionresults", (DemoService _service, bool acceptable) => {
    if(acceptable) {
        return Results.Ok(_service.NeedlesslyConsumeResources());
    }

    return Results.BadRequest("It's not okay to needlessly consume resources.");
});

Run the code via dotnet run in the terminal instance and navigate to localhost:5001/swagger

Additional Documentation

• .NET Preview 7 Announcement
• David Fowler's Minimal API repository