Add Results.Empty

[davidfowl]

Background and Motivation

Sometimes you want to return a result that does not mutate the response in anyway. This happens when you have multiple branches in a route handle and one of them should be a noop. You are forced to return an IResult and we don't have a built in result type that fills this role. Mvc has EmptyResult for this purpose.

Proposed API

namespace Microsoft.AspNetCore.Http
{
    public static class Results
    {
        public static IResult Empty(); // This could also be a property
    }
}

Usage Examples

app.MapGet("/{id}", (HttpContext context, string id) =>
{
    var httpProcessor = GetTargetStream(id);
    if (httpProcessor is null) return Results.NotFound();
 
    await httpProcessor.ProcessAsync(context);
     // Don't change what the httpProcessor did
    return Results.Empty();
});

Alternative Designs

Force people to write their own.

Risks

None

[ghost]

Thank you for submitting this for API review. This will be reviewed by @dotnet/aspnet-api-review at the next meeting of the ASP.NET Core API Review group. Please ensure you take a look at the API review process documentation and ensure that:

• The PR contains changes to the reference-assembly that describe the API change. Or, you have included a snippet of reference-assembly-style code that illustrates the API change.
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• Someone is assigned to "champion" this change in the meeting, and they understand the impact and design of the change.

[ghost]

Thanks for contacting us.

We're moving this issue to the .NET 7 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
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[pranavkm]

API review:

We'll use properties instead. Here's the approved API:

public static class Results
{
+   public static IResult Empty { get; } = new EmptyResult();
}

public class ControllerBase
{
+    public static EmptyResult Empty { get; } = new ();
}

[ShreyasJejurkar]

Hi @davidfowl @pranavkm, do we need to address this for MVC as well? I mean in property in ControllerBase??

[davidfowl]

Yep