ASP.NET Core equivalent of ASP.NET MVC 5's HttpException

Solution 1:

I implemented my own HttpException and supporting middleware which catches all HttpException's and turns them into the corresponding error response. A short extract can be seen below. You can also use the Boxed.AspNetCore Nuget package.

Usage Example in Startup.cs

public void Configure(IApplicationBuilder application)
{
    application.UseIISPlatformHandler();

    application.UseStatusCodePagesWithReExecute("/error/{0}");
    application.UseHttpException();

    application.UseMvc();
}

Extension Method

public static class ApplicationBuilderExtensions
{
    public static IApplicationBuilder UseHttpException(this IApplicationBuilder application)
    {
        return application.UseMiddleware<HttpExceptionMiddleware>();
    }
}

Middleware

internal class HttpExceptionMiddleware
{
    private readonly RequestDelegate next;

    public HttpExceptionMiddleware(RequestDelegate next)
    {
        this.next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        try
        {
            await this.next.Invoke(context);
        }
        catch (HttpException httpException)
        {
            context.Response.StatusCode = httpException.StatusCode;
            var responseFeature = context.Features.Get<IHttpResponseFeature>();
            responseFeature.ReasonPhrase = httpException.Message;
        }
    }
}

HttpException

public class HttpException : Exception
{
    private readonly int httpStatusCode;

    public HttpException(int httpStatusCode)
    {
        this.httpStatusCode = httpStatusCode;
    }

    public HttpException(HttpStatusCode httpStatusCode)
    {
        this.httpStatusCode = (int)httpStatusCode;
    }

    public HttpException(int httpStatusCode, string message) : base(message)
    {
        this.httpStatusCode = httpStatusCode;
    }

    public HttpException(HttpStatusCode httpStatusCode, string message) : base(message)
    {
        this.httpStatusCode = (int)httpStatusCode;
    }

    public HttpException(int httpStatusCode, string message, Exception inner) : base(message, inner)
    {
        this.httpStatusCode = httpStatusCode;
    }

    public HttpException(HttpStatusCode httpStatusCode, string message, Exception inner) : base(message, inner)
    {
        this.httpStatusCode = (int)httpStatusCode;
    }

    public int StatusCode { get { return this.httpStatusCode; } }
}

In the long term, I would advise against using exceptions for returning errors. Exceptions are slower than just returning an error from a method.

Solution 2:

After a brief chat with @davidfowl, it seems that ASP.NET 5 has no such notion of HttpException or HttpResponseException that "magically" turn to response messages.

What you can do, is hook into the ASP.NET 5 pipeline via MiddleWare, and create one that handles the exceptions for you.

Here is an example from the source code of their error handler middleware which will set the response status code to 500 in case of an exception further up the pipeline:

public class ErrorHandlerMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ErrorHandlerOptions _options;
    private readonly ILogger _logger;

    public ErrorHandlerMiddleware(RequestDelegate next, 
                                  ILoggerFactory loggerFactory,
                                  ErrorHandlerOptions options)
    {
        _next = next;
        _options = options;
        _logger = loggerFactory.CreateLogger<ErrorHandlerMiddleware>();
        if (_options.ErrorHandler == null)
        {
            _options.ErrorHandler = _next;
        }
    }

    public async Task Invoke(HttpContext context)
    {
        try
        {
            await _next(context);
        }
        catch (Exception ex)
        {
            _logger.LogError("An unhandled exception has occurred: " + ex.Message, ex);

            if (context.Response.HasStarted)
            {
                _logger.LogWarning("The response has already started, 
                                    the error handler will not be executed.");
                throw;
            }

            PathString originalPath = context.Request.Path;
            if (_options.ErrorHandlingPath.HasValue)
            {
                context.Request.Path = _options.ErrorHandlingPath;
            }
            try
            {
                var errorHandlerFeature = new ErrorHandlerFeature()
                {
                    Error = ex,
                };
                context.SetFeature<IErrorHandlerFeature>(errorHandlerFeature);
                context.Response.StatusCode = 500;
                context.Response.Headers.Clear();

                await _options.ErrorHandler(context);
                return;
            }
            catch (Exception ex2)
            {
                _logger.LogError("An exception was thrown attempting
                                  to execute the error handler.", ex2);
            }
            finally
            {
                context.Request.Path = originalPath;
            }

            throw; // Re-throw the original if we couldn't handle it
        }
    }
}

And you need to register it with StartUp.cs:

public class Startup
{
    public void Configure(IApplicationBuilder app, 
                          IHostingEnvironment env, 
                          ILoggerFactory loggerfactory)
    {
       app.UseMiddleWare<ExceptionHandlerMiddleware>();
    }
}