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<h1><a name="kanchor84"></a>Collections</h1>
<p>Internally the regular <span class="PrimaryPlattform">.NET</span>-collections are stored as arrays. When you store a collection, db4o will store all the collection-items into a array. And when you retrieve a collection, db4o will create a new instance of the collection and add back the items. <span class="PrimaryMap">Dictionary</span>-instances are stored as an array of key-values.</p>
<p>Unfortunately this implementation is not very efficient for searches/updates of a certain value in a collection, as the whole collection needs to be instantiated to access any of its elements.</p>
<p>db4o brings some special collections with it. There are collections which support transparent persistence. <a href="../../basics/activation_concept/transparent_activation_framework/Collections.htm" target="" title="" alt="" class="MCXref">See "TA Aware Collections"</a></p>
<p>When you have a need for a huge collection, you might run into some performance bottleneck, since collections are always stored and retrieved as complete unit. You can use db4o special big-set to improve performance. <a href="collections/big_set.htm" target="" title="" alt="" class="MCXref">See "Big Set"</a></p>
<p>You might wonder what is better to use, collection or arrays. Most of times it doesn't matter. <a href="collections/collections_or_arrays.htm" target="" title="" alt="" class="MCXref">See "Collections Or Arrays"</a></p>
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