Using context.Database.Log in MVC web app

Question

Using the guide here, I'm trying to log the SQL generated by my MVC web application.

The guide uses the line:

context.Database.Log = Console.Write;

Which obviously doesn't work with a web application. The guide described the Log property:

The DbContext.Database.Log property can be set to a delegate for any method that takes a string.

And it's this I don't understand, delegates just confuse me. How can I use this EF6 feature?

Answer 1

To write your logs to a file, try this:

using (var context = new MyDbContext())
{
    var logFile = new StreamWriter("C:\\temp\\log.txt");
    context.Database.Log = logFile.Write;

    // Execute your queries here
    // ....

    logFile.Close();
}

Answer 2

Using a delegate allows you to do write any function taking a string. As a very simple logging to a file, you could do the following:

context.Database.Log = message => File.AppendText("C:\\mylog.txt").WriteLine(message);

In a web environment, you may wish to use Trace to log this information:

context.Database.Log = message => Trace.WriteLine(message);

You can see more examples of using delegates on the MSDN page on Anonymous Functions.