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    copied!<p><strong>many-to-any</strong><br> If the table structure is fixed, and you want to use the <code>identity</code> id generator, I would map the Source tables as 3 separate classes and map to the common interface as an <a href="http://wiki.fluentnhibernate.org/Fluent_mapping#Any" rel="nofollow noreferrer">any</a> reference.</p> <pre><code>class Case { public virtual IReferral Referral { get; set; } } class SourceA : IReferral { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual string Type { get { return "SourceA"; } } } interface IReferral { int Id { get; set; } string Name { get; set; } string Type { get; } } public class CaseMap : ClassMap&lt;Case&gt; { public CaseMap() { ReferencesAny(m =&gt; m.Referral) .EntityTypeColumn("ReferralType") .EntityIdentifierColumn("ReferralId") .AddMetaValue&lt;SourceA&gt;("SourceA") .AddMetaValue&lt;SourceB&gt;("SourceB") .AddMetaValue&lt;SourceC&gt;("SourceC") .IdentityType&lt;int&gt;(); } } </code></pre> <p><strong>union-subclass</strong><br> Another option is <a href="http://nhforge.org/doc/nh/en/index.html#mapping-declaration-unionsubclass" rel="nofollow noreferrer">union-subclass</a> with an abstract base class mapping. This allows eager fetching, but you cannot use the <code>identity</code> generator on the subclass tables.</p> <pre><code>&lt;class name="IReferral" abstract="true" table="Referral"&gt; &lt;id name="Id"&gt; &lt;generator class="hilo"/&gt; &lt;/id&gt; &lt;property name="Name"/&gt; &lt;union-subclass name="SourceA" table="SourceA"&gt; &lt;!-- class specific properties --&gt; &lt;/union-subclass&gt; &lt;union-subclass name="SourceB" table="SourceB"&gt; &lt;!-- class specific properties --&gt; &lt;/union-subclass&gt; &lt;union-subclass name="SourceC" table="SourceC"&gt; &lt;!-- class specific properties --&gt; &lt;/union-subclass&gt; &lt;/class&gt; </code></pre> <p><strong>subclass</strong><br> If you can change the tables, you can map all 3 Referral classes to the same table using <a href="http://nhforge.org/doc/nh/en/index.html#mapping-declaration-subclass" rel="nofollow noreferrer">subclass</a>.</p> <pre><code>&lt;class name="IReferral" abstract="true" table="Referral" discriminator-value="null"&gt; &lt;id name="Id"&gt; &lt;generator class="identity"/&gt; &lt;/id&gt; &lt;discriminator column="Discriminator" not-null="true" type="System.String"/&gt; &lt;property name="Name"/&gt; &lt;subclass name="SourceA" discriminator-value="SourceA"&gt; &lt;!-- class specific properties --&gt; &lt;/subclass&gt; &lt;subclass name="SourceB" discriminator-value="SourceB"&gt; &lt;!-- class specific properties --&gt; &lt;/subclass&gt; &lt;subclass name="SourceC" discriminator-value="SourceC"&gt; &lt;!-- class specific properties --&gt; &lt;/subclass&gt; &lt;/class&gt; </code></pre>
 

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