Entity Framework 6 SaveChanges () Overrides Permanent Change Detection

Question

I expanded the class to add the last modified timestamp to the record if significant changes were made to it. This was done with code like this .

Here is my problem. SaveChanges()it starts for both changes, but the second does not fall into the loop: no object is detected as in need of changes.

However, the record is updated by EF through a call to base.SaveChanges ().

Here's an addendum to MasterTable:

namespace AuditTestEF
{
    public interface IHasAuditing
    {
        DateTime LastModifiedOn { get; set; }
        int LastModifiedBy { get; set; }
    }

    public partial class MasterTable : IHasAuditing
    {
    }

    public class AuditTestEntitiesWithAuditing : AuditTestEntities
    {
        public int TestingUserIs = 1;

        public override int SaveChanges()
        {
            foreach (ObjectStateEntry entry in (this as IObjectContextAdapter)
                .ObjectContext
                .ObjectStateManager
                .GetObjectStateEntries(EntityState.Added | EntityState.Modified))
            {
                // This loop is entered the first time, but not the second
                if (entry.IsRelationship) continue;

                var lastModified = entry.Entity as IHasAuditing;
                if (lastModified == null) continue;

                lastModified.LastModifiedOn = DateTime.UtcNow;
                lastModified.LastModifiedBy = TestingUserIs;
            }

            return base.SaveChanges();
        }
    }
}

And here is the test harness:

[TestMethod]
public void TestMethod1()
{
    MasterTable mtOriginal;
    using (var audit = new AuditTestEntitiesWithAuditing())
    {
        var message = "Hello";
        audit.TestingUserIs = 1;
        mtOriginal = new MasterTable {TextField = message};
        audit.MasterTable.Add(mtOriginal);
        audit.SaveChanges();
        // This test passes, TestingUser is set in the override
        Assert.IsTrue(mtOriginal.LastModifiedBy == audit.TestingUserIs);    
    }

    using (var audit = new AuditTestEntitiesWithAuditing())
    {
        var mt = audit.MasterTable.Find(mtOriginal.MasterTableId);
        mt.TextField = "Goodbye";
        audit.TestingUserIs = 4;
        audit.SaveChanges();
        // This test fails, the record is written with "Goodbye" but
        // GetObjectStateEntries(EntityState.Added | EntityState.Modified) has no entries.
        Assert.IsTrue(mt.LastModifiedBy == audit.TestingUserIs);            
    }
}

There is no other code. There is no weird disconnecting / tracking entity or anything else. WYSIWYG.

What am I missing? How is an explicitly modified object checked for Modified cleared?

Answer 1

... , , .

    public override int SaveChanges()
    {
        ChangeTracker.DetectChanges();

. , , - .