How to Get Error Details of an ASP.NET 5 app deployed on Azure Websites?

Question

I have an ASP.NET 5 solution with a website and several project libraries. I\'m using MVC 6 and Entity Framework 7. Locally the app is working fine and until today it was wo

Answer 1

Errors that occur in startup in an ASPNET5 application are really hard to track down when running the app in Azure (at least with beta 3). Hopefully they find a way to improve the experience. I had to resort to stripping my startup down to the bare bones and then adding code line by line until the failure happened (in my case, it was a missing environment variable).

I've also used code like this (for debugging only) which might help depending on where the error is happening:

public void Configure(IApplicationBuilder app, IHostingEnvironment env )
    {           
        try
        {                       
            // Add MVC to the request pipeline.
            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller}/{action}/{id?}"
                   );
            });
        }

//exceptions in startup are really bad when running in azure, all you will get is an internal server error
//this code will write the exception message to the browser instead.  Only use for debugging!!!

      catch (Exception ex)          
      {
            app.Run(async context =>
            {
                context.Response.ContentType = "text/plain";
                await context.Response.WriteAsync(ex.Message);
            });
        }
    }

Update 10/27/2016 A lot has changed since my original answer. The latest guidance is posted here:

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

So, add:

.CaptureStartupErrors(true) and .UseSetting(WebHostDefaults.DetailedErrorsKey, "true") on your WebHostBuilder like so:

 var host = new WebHostBuilder()
            .CaptureStartupErrors(true)
            .UseSetting(WebHostDefaults.DetailedErrorsKey, "true")
            .UseKestrel()
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseIISIntegration()
            .UseStartup()
            .Build();