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    <p>After hours of troubleshooting/trial and error, I've solved my problem. My POCO classes are also used in a disconnected environment, where the objects are detached from the context, modified, and then re-attached.</p> <p>In order to determine which navigation property collection items were affected, I overrode the Equals and GetHashCode methods in the Address class to determine equality. Apparently this affects the ability for EF 4.1 to insert a complete collection of navigation property objects???</p> <p>Here are the original equality methods which caused the issue:</p> <pre><code>public override bool Equals(object obj) { Address address = obj as Address; if (address == null) return false; return address.AddressId == this.AddressId; } public override int GetHashCode() { return this.AddressId.GetHashCode(); } </code></pre> <p>In order to correct the problem, I created a custom equality comparer for the navigation object rather than including it directly in the address class.</p> <pre><code>public class AddressEqualityComparer : IEqualityComparer&lt;Address&gt; { public bool Equals(Address address1, Address address2) { if (address1.AddressId == address2.AddressId) return true; else return false; } public int GetHashCode(Address address) { return address.AddressId.GetHashCode(); } } </code></pre> <p>My context.People.Add method call worked as expected after I made this change. </p> <p>If anyone knows why overriding the equality methods in the class causes EF 4.1 to only insert the first item in the collection, that would be great information.</p>
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    1. POEntity Framework 4.1 Code-First and Inserting New One-to-Many Relationships
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    1. POEntity Framework 4.1 Code-First and Inserting New One-to-Many Relationships
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    1. COInteresting. I could reproduce this and the problem occurs only when you override *both* methods. Can't explain exactly what's wrong, but one critical point is your implementation of `GetHashCode` imo. The problem is that it doesn't represent the object identity during the object's lifetime because when you create and add the object `AddressId` is 0 but when you call `SaveChanges` the Id changes to a value other than 0. Therefore the same object has suddenly another HashCode with your override. That's bad when objects are stored in dictionaries which might internally in EF be the case.
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    2. COWhen confronted with this issue I just added my own auxiliary hash code methods and left the standard .Net one be. One advantage to this is you can actually store these hashes in the DB for fast partial comparisons, like "Are these 20 fields the same between any two of these 30-field rows?"
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    3. COThat's because EF will handle the foreignkey collection and avoid duplicates by comparing objects in the navigational collection. In your case, all Address instances are new with the Id = 0, and you override the 'equal' method by comparing id, so EF thought your instances are all equal, then strip the others out but the first one.Hope this explains well.
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