ghstahl / aspdotnet-3-startup-logging

aspdotnet-3-startup-logging

ASP.NET Core 3.0 doesn't support logging in the Startup constructor or Startup.ConfigureServices as referenced in the following;
create-logs-in-the-startup-class

After reading Christian Riedl's [solution](LoggerBuffered on StackOverflow I adopted it. Later you will see that it works well when I embed the asp.net webapp inside an Azure Function.

The Solution

1. Create an in-memory ILogger that buffers the logs until we can hand them over to the real ILogger.
2. Defer any exception thrown before Startup.Configure to be thrown after we copy the in-memmory log to the real ILogger.
3. Only inject IServiceProvider into Startup.Configure as a means to get other services.

Dependency injects is built out after Startup.ConfigureServices completes, so you can inject services into Startup.Configure.
i.e.

 public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IMySuperDuperService msd, ILogger<Startup> logger)
 {
 
 
 }

This will blowup if an Exception is thrown in Startup.ConfigureServices before IMySuperDuperService was registered.

IServiceProvider and ILogger<Startup> will always be there, so just inject those and ask IServiceProvider for your IMySuperDuperService

public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IServiceProvider serviceProvider, ILogger<Startup> logger)
{
    ...
    var mySuperDuperService = serviceProvider.GetRequiredService<IMySuperDuperService>();
    ...
}

Azure Functions

When it comes to HTTP Trigger, I didn't want to learn another way to develop an app that was basically REST apis that required bearer token authorization. I use a technique that uses TestServer (of all things) to bridge the gap between request comming into the function and ultimately winding up being handled by a good ole asp.net core 3 app.

When it comes to logging, the azure function provides the initial logger which is turned into a LogProvider for the downstream asp.net core app.

Take a look at azFunc-logger where the shim is dotnetcore.azFunction.AppShim

Credits

LoggerBuffered
Christian Riedl