How do I view the SQL generated by the Entity Framework?

Question

How do I view the SQL generated by entity framework ?

(In my particular case I\'m using the mysql provider - if it matters)

Answer 1

My answer addresses EF core. I reference this github issue, and the docs on configuring DbContext:

Simple

Override the OnConfiguring method of your DbContext class (YourCustomDbContext) as shown here to use a ConsoleLoggerProvider; your queries should log to the console:

public class YourCustomDbContext : DbContext
{
    #region DefineLoggerFactory
    public static readonly LoggerFactory MyLoggerFactory
        = new LoggerFactory(new[] {new ConsoleLoggerProvider((_, __) => true, true)});
    #endregion


    #region RegisterLoggerFactory
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseLoggerFactory(MyLoggerFactory); // Warning: Do not create a new ILoggerFactory instance each time                
    #endregion
}

Complex

This Complex case avoids overriding the DbContext OnConfiguring method. , which is discouraged in the docs: "This approach does not lend itself to testing, unless the tests target the full database."

This Complex case uses:

• The IServiceCollection in Startup class ConfigureServices method (instead of overriding the OnConfiguring method; the benefit is a looser coupling between the DbContext and the ILoggerProvider you want to use)
• An implementation of ILoggerProvider (instead of using the ConsoleLoggerProvider implementation shown above; benefit is our implementation shows how we would log to File (I don't see a File Logging Provider shipped with EF Core))

Like this:

public class Startup

    public void ConfigureServices(IServiceCollection services)
    {
        ...
        var lf = new LoggerFactory();
        lf.AddProvider(new MyLoggerProvider());

        services.AddDbContext(optionsBuilder => optionsBuilder
                .UseSqlServer(connection_string)
                //Using the LoggerFactory 
                .UseLoggerFactory(lf));
        ...
    }
}

Here's the implementation of a MyLoggerProvider (and its MyLogger which appends its logs to a File you can configure; your EF Core queries will appear in the file.)

public class MyLoggerProvider : ILoggerProvider
{
    public ILogger CreateLogger(string categoryName)
    {
        return new MyLogger();
    }

    public void Dispose()
    { }

    private class MyLogger : ILogger
    {
        public bool IsEnabled(LogLevel logLevel)
        {
            return true;
        }

        public void Log(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func formatter)
        {
            File.AppendAllText(@"C:\temp\log.txt", formatter(state, exception));
            Console.WriteLine(formatter(state, exception));
        }

        public IDisposable BeginScope(TState state)
        {
            return null;
        }
    } 
}