In an application I have working with a needed to manually create a DbContext. But doing so, disabled all logging from the DbContext.

The problem

In most cases a DbContext is initialized via dependency injection. But I needed to customize which connection string to use. I did it like this:

CSharp 
string connectionString = ... ;

var dbContextOptionsBuilder =
    new DbContextOptionsBuilder<MyDatabaseContext>();

dbContextOptionsBuilder
    .UseSqlServer(connectionString);

var options = dbContextOptionsBuilder.Options;

return new MyDatabaseContext(options);

This works just fine. But a subtle change is that the DbContext will not be able to log anything.

The solution

It is not hard to fix just. Just make sure that the logging factory is setup via DbContextOptionsBuilder by calling UseLoggerFactory:

CSharp 
string connectionString = ... ;
ILoggerFactory loggerFactory = ... ;

var dbContextOptionsBuilder =
    new DbContextOptionsBuilder<MyDatabaseContext>();

dbContextOptionsBuilder
    .UseSqlServer(connectionString)
    .UseLoggerFactory(loggerFactory);

var options = dbContextOptionsBuilder.Options;

return new MyDatabaseContext(options);

Summary

I found this the hard way when I wanted to see exact which SQL statements were executed. I had enabled logging in my configuration file:

appsettings.json 
{
  "Logging": {
    "LogLevel": {
      "Microsoft.EntityFrameworkCore.Database.Command": "Information"
    }
  }
}

But still nothing was output. It worked for other DbContext which made me confused. Looking back, it was quite obvious. But it took a while for me for figure this out.