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POhow can I make nhibernate cascade save a set of objects with circular references?
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  1. POhow can I make nhibernate cascade save a set of objects with circular references?
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    copied!<p>I am assuming nhibernate can handle circular reference issues as I have not seen this mentioned otherwise in the docs or on google (but perhaps I have the wrong terms).</p> <p>Suppose I have a class which has as a member a reference to an instance of itself:</p> <p>e.g.</p> <pre><code>class A { A Other; } </code></pre> <p>I then create 2 objects and have them cross reference one another</p> <pre><code>A a1 = new A(); A a2 = new A(); a1.Other = a2; a2.Other = a1; </code></pre> <p>I want to produce a set of mappings for these classes such that if I attempt to save a in a session, it will also save b in such a way that b's reference to a is retained.</p> <p>At the moment I have produced a simple mapping using the many-to-one association (actually this is generated by fluent nhibernate but it looks OK on manual inspection)</p> <pre><code> &lt;hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-access=""&gt; &lt;class name="hibernate.experiment.CircularRefQn+A, hibernate.experiment, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="`A`" xmlns="urn:nhibernate-mapping-2.2"&gt; &lt;id name="Id" type="Int32" column="Id"&gt; &lt;generator class="identity" /&gt; &lt;/id&gt; &lt;many-to-one cascade="all" name="Other" column="Other_id" /&gt; &lt;/class&gt; &lt;/hibernate-mapping&gt; </code></pre> <p>But when I save, a1 does not save the reference to a2 in the database. How can I make it do this?</p> <p>example code using fluent nhibernate is here (requires nhibernate, fluent-nhibernate and nunit - if people want a stripped down version let me know).</p> <p>I also created an a3 object which refers to itself and this does not save as I would like.</p> <pre><code>using System.IO; using FluentNHibernate.Cfg; using FluentNHibernate.Mapping; using NHibernate.Tool.hbm2ddl; using NUnit.Framework; namespace hibernate.experiment { [TestFixture] public class CircularRefQn { [Test] public void Test() { var file = this.GetType().Name + ".db"; if (File.Exists(file)) File.Delete(file); var fcfg = Fluently.Configure() .Database(FluentNHibernate.Cfg.Db.SQLiteConfiguration.Standard .UsingFile(file)) .Mappings(m =&gt; { m.FluentMappings.Add(typeof(A.Map)); m.FluentMappings.ExportTo("."); }) .ExposeConfiguration(cfg =&gt; new SchemaExport(cfg).Create(true, true)) ; var sFactory = fcfg.BuildSessionFactory(); using (var s = sFactory.OpenSession()) { A a1 = new A(); A a2 = new A(); a1.Other = a2; a2.Other = a1; Assert.NotNull(a1.Other); Assert.NotNull(a2.Other); A a3 = new A(); a3.Other = a3; s.Save(a1); s.Update(a1); s.Save(a3); } using (var s = sFactory.OpenSession()) { foreach (var a in s.CreateCriteria(typeof(A)).List&lt;A&gt;()) Assert.NotNull(a.Other); } } public class A { public virtual int Id { get; set; } public virtual A Other { get; set; } public class Map : ClassMap&lt;A&gt; { public Map() { Id(x =&gt; x.Id); References(x =&gt; x.Other) .Cascade.All(); } } } } } </code></pre>
 

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