如何将 ILogger 注入 EFCore DbContext

Question

I have .net core app with EFCore db context:

public class MyappDbContext : DbContext
{
    private ILogger<MyappDbContext> _logger;

    public MyappDbContext(DbContextOptions<MyappDbContext> options)
        : base(options)
    {
        // ???
    }
}

In startup class I registered context:

services.AddDbContext<MyappDbContext>(options => options.UseSqlServer(connectionString));

How to inject into MyappDbContext , ILogger or ILoggerFactory (to create logger)?

Answer 1

All you need to do is add a ILoggerFactory or ILogger parameter to the context constructor:

public class MyappDbContext : DbContext
{
    private readonly ILogger<MyappDbContext> _logger;

    public MyappDbContext(DbContextOptions<MyappDbContext> options,
        ILogger<MyappDbContext> logger)
        : base(options)
    {
        _logger = logger;
    }
}

Answer 2

In case if you need to instantiate the dbcontext manually:

public class Startup
{
    public static readonly ILoggerFactory logFactory = LoggerFactory.Create(builder => builder.AddDebug());

    ....

    public Startup(IWebHostEnvironment env)
    {
        ....
    }
    public void ConfigureServices(IServiceCollection services)
    {
        ....
    }
}

public class MyDbContext : DbContext
{
    private readonly ILoggerFactory _loggerFactory;

    public MyDbContext(DbContextOptions<MyDbContext> options,
        ILoggerFactory loggerFactory)
        : base(options)
    {
        _loggerFactory = loggerFactory;
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseLoggerFactory(_loggerFactory);
        // optionsBuilder.EnableSensitiveDataLogging();
    }
}

// Somewhere else

var db = new MyDbContext(new DbContextOptions<MyDbContext>(), Startup.logFactory);

But I would recommend using DI instead:

public void ConfigureServices(IServiceCollection services)
{
            services.AddDbContext<MyDbContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("Default")).UseLoggerFactory(logFactory));
}