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Database Command Logging:

In this section, you will learn how to log commands & queries sent to the database by Entity Framework.

Prior to EF 6, we used the database tracing tool or third party tracing utility to trace database queries and commands sent by Entity Framework. Now, EF 6 provides a simple mechanism to log everything that Entity Framework is doing. It logs all the activity performed by EF using context.database.Log

You can attach any method of any class, which accepts one string parameter and returns void.

In the following example, we use Console.Write method to log EF activities:

using (var context = new SchoolDBEntities())
{
    context.Database.Log = Console.Write;
    var student = context.Students
                        .Where(s => s.StudentName == "Student1").FirstOrDefault<Student>();

    student.StudentName = "Edited Name";
    context.SaveChanges();
}

Output:

You can see in the output that it logs all the activities performed by EF, e.g. opening & closing connection, execution & completion time and database queries & commands.

Context.Database.Log is an Action<string> so that you can attach any method which has one string parameter and void return type. For example:

public class Logger
{
        public static void Log(string message)
        {
            Console.WriteLine("EF Message: {0} ", message);
        }
}

class EF6Demo
{
    
        public static void DBCommandLogging()
        {
            using (var context = new SchoolDBEntities())
            {
                
                context.Database.Log =  Logger.Log;                
                var student = context.Students
                                .Where(s => s.StudentName == "Student1").FirstOrDefault<Student>();

                student.StudentName = "Edited Name";
                context.SaveChanges();
            }
        }
}

Download DB First sample project for DB command logging demo.

Entity Framework 6.0 Tutorials（4）：Database Command Logging

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原文地址：http://www.cnblogs.com/purplefox2008/p/5649531.html