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POBidi associations and NHibernate mapping
 

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    <p>I have classes BidiParent and BidiChildList which link parents and children in a bidirectional parent-child relationship. If a child's parent is updated by e.g. the service layer, the old and new parents' children lists are automatically updated to reflect the change. Likewise, if a parent's children list is updated by e.g. adding a new child, the child's parent is automatically changed as is the old parent's children list. I want to try to build up a "smart" domain model.</p> <p>First question, obviously, is: is this even a good idea?</p> <p>Second question is: is it possible to tell NHibernate to access and modify the <em>field</em> _Children or _Parent, but to consider the <em>property</em> Children or Parent to be entirely synonymous with the field? That NHibernate should load and save the internal fields, but HQL or LINQ queries should use the public properties?</p> <pre><code>public class BidiParent&lt;C, P&gt; { ... } public class BidiChildList&lt;C, P&gt; : IList&lt;C&gt; { ... } public class Parent { public string Name { get; set; } public IList&lt;Child&gt; Children { get { return ChildrenBidi; } set { ChildrenBidi.Set(value); } } private BidiChildList&lt;Child, Parent&gt; ChildrenBidi { get { return BidiChildList.Create(this, p =&gt; p._Children, c =&gt; c._Parent, (c, p) =&gt; c._Parent = p); } } internal IList&lt;Child&gt; _Children = new List&lt;Child&gt;(); } public class Child { public string Name { get; set; } public Parent Parent { get { return ParentBidi.Get(); } set { ParentBidi.Set(value); } } private BidiParent&lt;Child, Parent&gt; ParentBidi { get { return BidiParent.Create(this, p =&gt; p._Children, () =&gt; _Parent, p =&gt; _Parent = p); } } internal Parent _Parent = null; } [Test] public void MultilevelConstruction_Succeeds() { var p = new Parent { Name = "Bob", Children = new List&lt;Child&gt; { new Child { Name = "Kate" }, new Child { Name = "Billy" } } }; Assert.AreEqual(2, p.Children.Count); Assert.AreEqual("Kate", p.Children[0].Name); Assert.AreEqual("Billy", p.Children[1].Name); Assert.AreSame(p, p.Children[0].Parent); Assert.AreSame(p, p.Children[1].Parent); } </code></pre>
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