ASP.NET Core Tips & Tricks

Startup.cs

public class Startup
{
  private const string ExceptionsOnStartup = "Startup";
  private const string ExceptionsOnConfigureServices = "ConfigureServices";

  private readonly Dictionary<string, List<Exception>> _exceptions;

  public Startup(IHostingEnvironment env, IApplicationEnvironment appEnv, ILoggerFactory logger, string[] args = null)
  {
    this._exceptions = new Dictionary<string, List<Exception>>
                           {
                             { ExceptionsOnStartup, new List<Exception>() },
                             { ExceptionsOnConfigureServices, new List<Exception>() },
                           };

    try
    {
      ...
    }
    catch (Exception ex)
    {
      this._exceptions[ExceptionsOnStartup].Add(ex);
    }
  }

  ...

  public IServiceProvider ConfigureServices(IServiceCollection services)
  {
    try
    {
      ...
    }
    catch (Exception ex)
    {
      this._exceptions[ExceptionsOnConfigureServices].Add(ex);
      return null;
    }
  }

  public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory logger)
  {
    logger.AddConsole(this.Configuration.GetSection("Logging"));
    logger.AddDebug();

    var log = logger.CreateLogger<Startup>();
    if (this._exceptions.Any(p => p.Value.Any()))
    {
      app.Run(
        async context =>
          {
            context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
            context.Response.ContentType = "text/plain";

            foreach (var ex in this._exceptions)
            {
              foreach (var val in ex.Value)
              {
                log.LogError($"{ex.Key}:::{val.Message}");
                await context.Response.WriteAsync($"Error on {ex.Key}: {val.Message}").ConfigureAwait(false);
              }
            }
          });
      return;
    }

    ...
  }
}