C# - An ObjectResult that when executed will produce a Too Many Requests (429) response with an optional Retry-After header.

TooManyRequestsObjectResult.cs

namespace Microsoft.AspNetCore.Mvc;

/// <summary>
/// An <see cref="ObjectResult"/> that when executed will produce
/// a <see cref="StatusCodes.Status429TooManyRequests"/> response
/// with an optional Retry-After header.
/// </summary>
[DefaultStatusCode(DefaultStatusCode)]
public class TooManyRequestsObjectResult : ObjectResult
{
    private const int DefaultStatusCode = StatusCodes.Status429TooManyRequests;
    public TimeSpan? RetryAfter { get; }

    public TooManyRequestsObjectResult([ActionResultObjectValue] object value)
        : base(value)
    {
        StatusCode = DefaultStatusCode;
    }

    public TooManyRequestsObjectResult([ActionResultObjectValue] object value, int retryAfter)
        : this(value, TimeSpan.FromSeconds(retryAfter))
    {
    }

    public TooManyRequestsObjectResult([ActionResultObjectValue] object value, TimeSpan retryAfter)
        : this(value)
    {
        if (retryAfter < TimeSpan.Zero)
        {
            throw new ArgumentOutOfRangeException(nameof(retryAfter), $"{nameof(retryAfter)} must be a non negative value");
        }

        RetryAfter = retryAfter;
    }

    public override Task ExecuteResultAsync(ActionContext context)
    {
        ArgumentNullException.ThrowIfNull(context);

        if (RetryAfter.HasValue)
        {
            context.HttpContext.Response.Headers.RetryAfter = Math.Round(RetryAfter.Value.TotalSeconds).ToString();
        }

        return base.ExecuteResultAsync(context);
    }
}