Design validation for Minimal APIs

Idea:

// Step 5: Input validation
app.MapPost("/todos", async (Validated<Todo> inputTodo, TodoDb db) =>
{
    var (todo, isValid) = inputTodo;
    if (!isValid) return Problem(inputTodo);

    db.Todos.Add(todo);
    await db.SaveChangesAsync();

    return CreatedAt(routes.GetTodo.Url(todo.Id), todo);
};

From: https://github.com/dotnet/aspnetcore/issues/30580

[davidfowl]

In .NET 7 you’ll be able to write a filter that can run validation on all the parameters trivially. In fact @DamianEdwards, you should add that filter to the Minimal.Extensions.

I was convinced, In your opinion, if we change MVC validations In a way that only validate IValidatable objects and optimize this changes in MinimalApis Is this possible?

MVC already has a validation system so we wouldn’t change it. It does what it does. As for minimal APIs, doing it by default means we need to have an abstraction so others can plug in (for things like fluent validation etc) or a way to turn it off. The way I see it the extensibility point for plugging in validation is filters, so you can plug in to do it automagically.

[DamianEdwards]

Doing some “customer research” https://twitter.com/DamianEdwards/status/1486871181252833284

Result: