MVC 6 HttpResponseException

Question

I am trying to return status codes in the following way

throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.Unauthorized) { ReasonPhrase = "invalid username/password" });

now this is not supported in MVC6, which sucks because using IActionResult seems really silly to me, and way less intuitive. I have found the following posts one and two. the first leads to a broken link, and the second applies to an MVC application.

I did realize that I need to create a middleware to address this issue, but I am not sure where to start, and since this is pretty useful stuff, I would expect there to be some open source solution I could use or maybe a code snippet.

For the record, I am using ASP.net 5 rc1 update 1 MVC 6

Answer 1

I think this change is due to .NET Core - where ASP.NET tries to do everything out of the box, ASP.NET Core only does what you specifically tell it to (which is a big part of why it's so much quicker and portable).

If you want this behaviour in Core you need to add it, either as a package that someone has written for you or by rolling your own.

It's fairly simple. First you need a custom exception to check for:

public class StatusCodeException : Exception
{
    public StatusCodeException(HttpStatusCode statusCode)
    {
        StatusCode = statusCode;
    }

    public HttpStatusCode StatusCode { get; set; }
}

Then you need a RequestDelegate handler that checks for the new exception and converts it to the HTTP response status code:

public class StatusCodeExceptionHandler
{
    private readonly RequestDelegate request;

    public StatusCodeExceptionHandler(RequestDelegate next)
    {
        this.request = next;
    }

    public Task Invoke(HttpContext context) => this.InvokeAsync(context); // Stops VS from nagging about async method without ...Async suffix.

    async Task InvokeAsync(HttpContext context)
    {
        try
        {
            await this.request(context);
        }
        catch (StatusCodeException exception)
        {
            context.Response.StatusCode = (int)exception.StatusCode;
            context.Response.Headers.Clear();
        }
    }
}

Then you register this middleware in your startup:

public class Startup
{
    ...

    public void Configure(IApplicationBuilder app)
    {
        ...
        app.UseMiddleware<StatusCodeExceptionHandler>();

Finally you can throw the HTTP status code exception in your actions, while still returning an explicit type that you can easily unit test:

public Thing Get(int id) {
    Thing thing = GetThingFromDB();

    if (thing == null)
        throw new StatusCodeException(HttpStatusCode.NotFound);

    return thing;
}

This is fairly simple and someone out there has probably written a more complete one, but I haven't been able to find one or get a clear answer as to why this was dropped.