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PONHibernate configuration for uni-directional one-to-many relation
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  1. PONHibernate configuration for uni-directional one-to-many relation
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    copied!<p>I'm trying to set up a relationship as follows. Each <strong>Master</strong> item has one or more <strong>Detail</strong> items:</p> <pre><code>public class Detail { public virtual Guid DetailId { get; set; } public virtual string Name { get; set; } } public class Master { public virtual Guid MasterId { get; set; } public virtual string Name { get; set; } public virtual IList&lt;Detail&gt; Details { get; set; } } </code></pre> <p>And Mappings:</p> <pre><code>public class MasterMap : ClassMap&lt;Master&gt; { public MasterMap() { Id(x =&gt; x.MasterId); Map(x =&gt; x.Name); HasMany(x =&gt; x.Details).Not.KeyNullable.Cascade.All(); } } public class DetailMap : ClassMap&lt;Detail&gt; { public DetailMap() { Id(x =&gt; x.Id); Map(x =&gt; x.Name); } } </code></pre> <p>The <strong>Master</strong> database table is:</p> <pre><code>masterId uniqueidentifier NOT NULL name nvarchar(max) NULL </code></pre> <p>and <strong>Detail</strong> is:</p> <pre><code>DetailId uniqueidentifier NOT NULL name nvarchar(max) NULL MasterId uniqueidentifier NULL foreign key (masterId) references [Master] </code></pre> <p>I don't really care to have a link from Detail back to Master -- in otherwords, Detail objects on their own are just not interesting to my domain layer. They will <em>always</em> be accessed via their Master object.</p> <p>Using code like this:</p> <pre><code>Master mast = new Master { MasterId = new Guid(), Name = "test", Details = new List&lt;Detail&gt; { new Detail { .DetailId = new Guid(), .Name = "Test1" }, new Detail { .DetailId = new Guid(), .Name = "Test1" } } }; using (transaction == Session.BeginTransaction) { Session.Save(mast); transaction.Commit(); } </code></pre> <p>This works great, except for a crazy limitation outlined in <a href="https://stackoverflow.com/questions/554674/fluent-nhibernate-one-to-many-uni-directional-mapping">this post</a>: NHibernate does an INSERT and puts Detail.MasterId as NULL first, then does an UPDATE to set it to the real MasterId.</p> <p>Really, I don't want Detail entries with NULL MasterIds, so if I set the MasterId field to NOT NULL, the INSERT to Detail will fail, because as I said NHibernate is trying to put in MasterId = NULL. </p> <p>I guess my question boils down to this:</p> <p>How can I get the above code sample to work with my existing domain model (eg, without adding a Detail.Master property), and the Detail.MasterId field in the database set to NOT NULL?</p> <p>Is there a way to get Nhibernate to just put the correct MasterId in the initial INSERT, rather than running an UPDATE afterwards? Is there rationale somewhere for this design decision? -- I'm struggling to see why it would be done this way.</p>
 

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