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POUsing 'Assigned' ID with NHibernate
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  1. POUsing 'Assigned' ID with NHibernate
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    copied!<p>I have two entities, <strong>Job</strong> and <strong>Language</strong>, in a many-to-one relationship. The mapping configuration of these entities is as follows:</p> <pre><code>public class JobMap : ClassMap&lt;Job&gt; { public JobMap() { Table("\"JOB\""); LazyLoad(); Id(x =&gt; x.Id, "id").GeneratedBy.HiLo("hilo", "hilo_job", "50"); Map(x =&gt; x.Name).Column("name").Unique(); References&lt;Language&gt;(x =&gt; x.SourceLanguage, "fk_id_language").Cascade.None(); } } public class LanguageMap : ClassMap&lt;Language&gt; { public LanguageMap() { Table("\"LANGUAGE\""); LazyLoad(); Id(x =&gt; x.Id, "id").GeneratedBy.Assigned().UnsavedValue(0); Map(x =&gt; x.Code).Column("code"); } } </code></pre> <p>I use this code to add a job into the database</p> <pre><code>private IServiceOperationResult AddJob(string jobName, Language sourceLanguage) { try { ISession session = sessionBuilder.GetSession(); using (ITransaction transaction = session.BeginTransaction(System.Data.IsolationLevel.Serializable)) { job = new Job(jobName, sourceLanguage); jobRepository.Add(job); transaction.Commit(); } } catch (Exception e) { log.Error("Error adding job to the DB", e); return new StringServiceOperationResult(e); } return new OkOperationResult(); } </code></pre> <p>The <strong>JobRepository.Add(Job job</strong>) is simple</p> <pre><code>public void Add(Job entity) { SessionBuilder.GetSession().Save(entity); } </code></pre> <p>The problem is that running this code with NHProfiler on, I can see the following warning before <strong>INSERT</strong> into the <strong>JOB</strong> table:</p> <blockquote> <p>WARN: Unable to determine if en-GB with assigned identifier 47 is transient or detached; querying the database. Use explicit Save() or Update() in session to prevent this.</p> </blockquote> <p>followed by (unnecessary) <strong>SELECT</strong> from the <strong>LANGUAGE</strong> table to load the <strong>Language</strong> entity with the id 47 (where "en-GB" is a code of a <strong>Job.SourceLanguage</strong> object).</p> <p>In my case I do not want to ever update, insert or delete a <strong>Language</strong> entity from the database (in situation where it is just referenced from other entities), it is really immutable table, filled with the correct rows all the time. Is there a way to tell NHibernate to just take the <strong>Language</strong> from me and when inserting into the <strong>JOB</strong> table, to use its <strong>Id</strong> property and not care whether it is present in the database or not?</p> <p>When I add this line before adding the <strong>Job</strong> to the repository</p> <pre><code>job.SourceLanguage = session.Load&lt;Language&gt;(sourceLanguage.Id); </code></pre> <p>I no longer get the warning nor the <strong>SELECT</strong>, but it is kind of cumbersome to do this everywhere I work with the <strong>Language</strong> entity.</p> <p>Thank you very much.</p>
 

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