Entity Framework Original Value not as expected - entity-framework

Question

In the following code I expect the Original Value to be different to the new value that I have set.
Why does my test fail? I am using EF 6.1.0
The Original Value is being incorrectly set to the new value.
[TestMethod]
public void CheckOriginalAndNew()
{
var dbContext = new ProjectContext();
var proj = dbContext.Projects.Find( 1);
proj.Description = Guid.NewGuid().ToString();
DbSet<Project> dbSet = dbContext.Set<Project>();
dbSet.Add(proj);
foreach (var entry in dbContext.ChangeTracker.Entries())
{
entry.State = System.Data.Entity.EntityState.Modified;
}
ObjectContext objectContex = ((IObjectContextAdapter)dbContext).ObjectContext;
objectContex.DetectChanges();
var entries =
objectContex.ObjectStateManager.GetObjectStateEntries(System.Data.Entity.EntityState.Modified);
foreach (ObjectStateEntry entry in entries.Where(e => e.Entity is LoggedEntity && !e.IsRelationship))
{
for (int i = 0; i < entry.CurrentValues.FieldCount; i++)
{
string fieldName = entry.CurrentValues.DataRecordInfo.FieldMetadata[i].FieldType.Name;
int ordinal = entry.OriginalValues.GetOrdinal(fieldName);
if (fieldName == "Description")
{
object newValue = entry.CurrentValues[ordinal];
object oldValue = entry.OriginalValues[ordinal];
Assert.AreNotEqual(newValue, oldValue); // fails! Why?
}
}
}
}

Answer 1

The reason the original value matches the current value is that the entry has been added instead of modified.
Instead of
DbSet<Project> dbSet = dbContext.Set<Project>();
dbSet.Add(proj);
I should have used
dbContext.Entry(proj).State = System.Data.Entity.EntityState.Modified;