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POHow to map correctly over two tables in hibernate
 

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    <p>I have two Mapping files. Building and ContactPerson. Each Buildung has one ContactPerson. So i have done a one-to-one relationship</p> <p>In Building i have the column "Meetingplace" and in Contact i have the columns "Meetingplace" and "ContactpersonName"</p> <p>In Contact i assign a Contactperson to a Meetingplace. </p> <p>For example: Meetingplace in Building is Germany. Now in Contact i assign a Contactperson to Meetingplace Germany. </p> <p>Contact:</p> <p>Here are my Mappingfiles</p> <pre><code> &lt;class name="Book.Doa.Contact" table="Contact"&gt; &lt;id name="ID"&gt; &lt;generator class="foreign"&gt; &lt;param name="property"&gt;Parent&lt;/param&gt; &lt;/generator&gt; &lt;/id&gt; &lt;property name="Contact" length="20" column="Contactperson"/&gt; &lt;property name="Meeting" length="20" column="Meetingplace"/&gt; &lt;one-to-one name="Parent" class="Book.Doa.Building" constrained="true"/&gt; </code></pre> <p>Building:</p> <pre><code> &lt;class name="Book.Doa.Building"&gt; &lt;id name="ID"&gt; &lt;generator class="native"&gt; &lt;param name="sequence"&gt;GLOBALSEQUENCE&lt;/param&gt; &lt;/generator&gt; &lt;/id&gt; &lt;property name="Standort" column="Meetingplace" /&gt; &lt;one-to-one name="Partner" lazy="false" cascade="all" fetch="join" outer-join="true" class="BookIt.Domain.Contact, BookIt.Core" /&gt; &lt;/class&gt; </code></pre> <p>My problem ist that iam geeting alwas the Error: </p> <pre><code>Object reference not set to instance of an object </code></pre> <p>if i use room.Building.Partner.Contact to get the Contactperson for Meetingplace in Building.</p> <p>There are values in the Database so i dont know why iam getting that error. What iam doing wrong? The Questions is how can i get the ContactPerson for the Meetingplace in Bulding?</p> <p>Please Help! .</p>
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    1. COI've seen your German version, and could not find out what is wrong. But this translated version seem to be more broken. E.g. `room.Building.Contact` ... cannot work because your mapping says: `Building.Partner`. Could you show C# mapping? and the query you call resulting in null exception, please?
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      1. USRadim Köhler
 

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