Entity Framework – AutoDetectChangesEnabled

From MSDN

When using most POCO entities the determination of how an entity has changed (and therefore which updates need to be sent to the database) is handled by the Detect Changes algorithm. Detect Changes works by detecting the differences between the current property values of the entity and the original property values that are stored in a snapshot when the entity was queried or attached. The techniques shown in this topic apply equally to models created with Code First and the EF Designer.

But some times we need to turn off this feature. for example, I need to upload a excel file it contains a bulk data. At this time AutoDetectChangesEnabled is true then it take a lot time for insert all rows. I can do the data validations at db side.

Just check the difference of AutoDetectChangesEnabled ON and OFF while inserting a bulk data.

Normal way:

namespace TestAutoDetectChangesEnabled
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Title = "Time Test - AutoDetectChangesEnabled";
            string[] names = { "Arun", "Raj", "Musthaan", "Majeed", "Muzafir",
                                 "Hari", "Dharma", "Kannan", "Imran", "Santo",
                                 "Rahmath", "Jayesh" };
            Stopwatch sw = new Stopwatch();
            sw.Start();
            var db = new AppContext();
            foreach (var i in Enumerable.Range(1, 20000))
            {
                var student = new Student()
                {
                    Name = names[(new Random().Next(0, 10))],
                    ContactNo = "9870002735",
                    RegNo = i.ToString().PadLeft(7, '0')
                };
                db.Students.Add(student);
                Console.Clear();
                Console.WriteLine("{0} records added", i);
            }
            db.SaveChanges();
            sw.Stop();
            Console.WriteLine("Taked time - {0}", sw.ElapsedMilliseconds);
            Console.ReadKey();
        }
    }

    public class AppContext : DbContext
    {
        public AppContext()
            : base("AppConnection")
        {

        }
        public DbSet<Student> Students { get; set; }
    }
    public class Student
    {
        public long Id { get; set; }
        public string Name { get; set; }
        public string RegNo { get; set; }
        public string ContactNo { get; set; }

    }
}

AutoDetectChangesEnabled-before

After disable AutoDetectChanges

 class Program
    {
        static void Main(string[] args)
        {
            Console.Title = "Time Test - AutoDetectChangesEnabled";
            string[] names = { "Arun", "Raj", "Musthaan", "Majeed", "Muzafir",
                                 "Hari", "Dharma", "Kannan", "Imran", "Santo",
                                 "Rahmath", "Jayesh" };
            Stopwatch sw = new Stopwatch();
            sw.Start();
            var db = new AppContext();
            try
            {
                db.Configuration.AutoDetectChangesEnabled = false;

                foreach (var i in Enumerable.Range(1, 20000))
                {
                    var student = new Student()
                    {
                        Name = names[(new Random().Next(0, 10))],
                        ContactNo = "9870002735",
                        RegNo = i.ToString().PadLeft(7, '0')
                    };
                    db.Students.Add(student);
                    Console.Clear();
                    Console.WriteLine("{0} records added", i);
                }
                db.SaveChanges();
            }
            finally
            {
                db.Configuration.AutoDetectChangesEnabled = true;
            }
            sw.Stop();
            Console.WriteLine("Taked time - {0}", sw.ElapsedMilliseconds);
            Console.ReadKey();
        }
    }

AutoDetectChangesEnabled-after

See the difference, it almost 10x faster. But use it with care. Don’t forget to re-enable detection of changes after the loop — used a try/finally to ensure it is always re-enabled even if code in the loop throws an exception.

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See System.Data.Entity.Validation.DbEntityValidationException Details

Today i got an error on saving data to db using EF.

An exception of type ‘System.Data.Entity.Validation.DbEntityValidationException’ occurred in EntityFramework.dll but was not handled in user code

Additional information: Validation failed for one or more entities. See ‘EntityValidationErrors’ property for more details.

System.Data.Entity.Validation.DbEntityValidationException

but I can’t find out what are the failed validations.

System.Data.Entity.Validation.DbEntityValidationException2

No more details in quick watch. I stucked a little. At this time i find out the use of $exception.That is a special debugger variable. You cannot access it via code.

https://msdn.microsoft.com/en-us/library/ms164891.aspx

https://blogs.msdn.microsoft.com/shaykatc/2004/02/20/vs-2003-tip-3-view-exception-information-with-exception/

look  $exception in quickwatch.

System.Data.Entity.Validation.DbEntityValidationException3