How does one use Elmah in ASP.NET 5/vNext/Core?

Question

I am a bit confused about how to use Elmah in the ASP.NET 5 / MVC 6 projects. I got the package from nuget and it added "Elmah.Mvc": "2.1.2" to dependencies in project.json.

I am not sure where to go from here - back in the day, nuget would add entries to the web.config which is now gone. And I can't seem to find any examples on their github or elsewhere.

Am I missing something simple?

Answer 1

Instead of using ELMAH, it's not hard to implement error logging manually. This process will catch any exception that occurs in the project and log it to a database table. To do this, add the following to the Configure method in Startup.cs

  if (env.IsDevelopment())
  {
    app.UseDeveloperExceptionPage();
    app.UseBrowserLink();
  }
  else
  {
    app.UseExceptionHandler(builder =>
      {
        builder.Run(async context =>
        {
          context.Response.StatusCode = (int)System.Net.HttpStatusCode.InternalServerError;
          context.Response.ContentType = "text/html";

          var error = context.Features.Get<Microsoft.AspNetCore.Diagnostics.IExceptionHandlerFeature>();
          if (error != null)
          {
            LogException(error.Error, context);
            await context.Response.WriteAsync("<h2>An error has occured in the website.</h2>").ConfigureAwait(false);
          }
        });
      });
  }

Include this in Startup.cs as well:

private void LogException(Exception error, HttpContext context)
{
  try
  {
    var connectionStr = Configuration["ConnectionString"];
    using (var connection = new System.Data.SqlClient.SqlConnection(connectionStr))
    {
      var command = connection.CreateCommand();
      command.CommandText = @"INSERT INTO ErrorLog (Application, Host, Type, Source, Path, Method, Message, StackTrace, [User],  WhenOccured)
    VALUES (@Application, @Host, @Type, @Source, @Path, @Method, @Message, @StackTrace, @User,  @WhenOccured)";
      connection.Open();

      if (error.InnerException != null)
        error = error.InnerException;

      command.Parameters.AddWithValue("@Application", this.GetType().Namespace);
      command.Parameters.AddWithValue("@Host", Environment.MachineName);
      command.Parameters.AddWithValue("@Type", error.GetType().FullName);
      command.Parameters.AddWithValue("@Source", error.Source);
      command.Parameters.AddWithValue("@Path", context.Request.Path.Value);
      command.Parameters.AddWithValue("@Method", context.Request.Method);
      command.Parameters.AddWithValue("@Message", error.Message);
      command.Parameters.AddWithValue("@StackTrace", error.StackTrace);
      var user = context.User.Identity?.Name;
      if (user == null)
        command.Parameters.AddWithValue("@User", DBNull.Value);
      else
        command.Parameters.AddWithValue("@User", user);
      command.Parameters.AddWithValue("@WhenOccured", DateTime.Now);

      command.ExecuteNonQuery();
    }
  }
  catch { }
}

Note that you will have to create a table in your database with the structure used in this function.