ASP.NET 5 API return exception to caller

Question

I'm switching from ASP.NET 4.5 to ASP.NET 5 and am using it to generate some RESTful web services. In 4.5 I was able to throw an exception inside of an action and have it get back to the caller. I want to do that in ASP.NET 5, but I have had no luck doing so yet. I want to avoid using a Try/Catch on every action to accomplish this.

ASP.NET information from Visual Studio about window: ASP.NET and Web Tools 2015 (RC1 Update 1) 14.1.11120.0

Here is an example of the code I'm using to test this.

[Route("[controller]")]
public class SandController : Controller
{
    /// <summary>
    /// Test GET on the webservice.
    /// </summary>
    /// <returns>A success message with a timestamp.</returns>
    [HttpGet]
    public JsonResult Get()
    {
        object TwiddleDee = null;
        string TwiddleDum = TwiddleDee.ToString();

        return Json($"Webservice successfully called on {DateTime.Now}.");
    }
}

I'm able to call this action and see my breakpoint hit, but on the calling end I receive a 500 error code and no body in the response.

Edit 1:

I changed my example to reflect this, but I want to return the exception information to a caller in the situation I have an unexpected exception, not one I have thrown myself. The code is an example, I'm aware that particular situation could be solved by a null ref check.

Edit 2:

@danludwig pointed out MSDN documentation for middleware which generated this solution:

private void ConfigureApp(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();

    app.UseIISPlatformHandler();

    app.UseStaticFiles();

    // Adding middleware to catch exceptions and handle them
    app.Use(async (context, next) =>
    {
        try
        {
            await next.Invoke();
        }
        catch (Exception ex)
        {
            context.Response.WriteAsync($"FOUND AN EXCEPTION!: {ex.Message}");
        }
    });

    app.UseMvc();
}

Answer 1

I want to avoid using a Try/Catch on every action to accomplish this.

https://docs.asp.net/en/latest/fundamentals/middleware.html

Note that middleware also means you don't need to add any ExceptionFilterAttribute s

Answer 2

You can achieve that by using an ExceptionFilterAttribute . You will need one for each type of exception that you want to catch. You then need to register it in FilterConfig.cs

public class RootExceptionFilterAttribute : ExceptionFilterAttribute 
{
    public override void OnException(HttpActionExecutedContext context)
    {
        if (context.Exception is Exception)
        {
            context.Response = new HttpResponseMessage(HttpStatusCode.InternalServerError);
            // or...
            // context.Response.Content = new StringContent("...");
            // context.Response.ReasonPhrase = "random";
        }
    }
}