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POHow to find out if an Entity Framework object has changed?
 

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  1. POHow to find out if an Entity Framework object has changed?
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    <p>I've an object which is called <code>Uczestnik</code> which just got saved to database </p> <pre><code>var konsultant = uczestnik.Konsultanci; uczestnik.Konsultanci = null; // null attached object and reuse it's ID later on for SAVE purposes uczestnik.KonsultantNazwa = konsultant.KonsultantNazwa; uczestnik.Szkolenie = null; // null attached object and reuse it's ID later on for SAVE purposes uczestnik.SzkolenieID = szkolenie.SzkolenieID; context.SzkolenieUczestnicies.AddObject(uczestnik); context.SaveChanges(); context.Detach(uczestnik); // detatch to prevent Context problems uczestnik.Szkolenie = szkolenie;// reassign for use in ObjectListView uczestnik.Konsultanci = konsultant; // reassign for use in ObjectListView </code></pre> <p>After it's saved it's back into ObjectListView where user decided to change some value and the value was changed (one value from multiple to be exact). If I check value's entity state it's in Unchanged state so calling .Attach and .SaveChanges() won't do anything. I can use <code>ChangeObjectState</code> but if there's nothing changed then there's no sense to do so.</p> <pre><code>context.SzkolenieUczestnicies.Attach(uczestnik); //context.ObjectStateManager.ChangeObjectState(uczestnik, EntityState.Modified); context.SaveChanges(); </code></pre> <p>How can I detect the change and prevent unnecessary traffic (I can imagine situation where nothing is changed in the object that holds files 5mb big) so <code>resaving</code> it makes no sense. Unless Entity is smart enough to detect that only one field was changed from 15 and change only that field? </p>
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    1. USMadBoy
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    1. COHave you looked at ObjectContext.DetectChanges?
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      1. USAaron McIver
    2. CONo, wasn't aware of it? How would I use it? Also considering that context is enclosed in `using` wouldn't DetectChanges show nothing when it's executed on new context?
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