<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns:MadCap="http://www.madcapsoftware.com/Schemas/MadCap.xsd" MadCap:lastBlockDepth="2" MadCap:lastHeight="120" MadCap:lastWidth="624" MadCap:disableMasterStylesheet="true" MadCap:tocPath="Advanced Features|Refactoring And Schema Evolution|Refactoring Class Hierarchy" MadCap:InPreviewMode="false" MadCap:RuntimeFileType="Topic" MadCap:TargetType="WebHelp" MadCap:PathToHelpSystem="../../../../" MadCap:HelpSystemFileName="index.xml" MadCap:SearchType="Stem">
<head><title>Removing Class From A Hierarchy</title>
<script type="text/javascript">/* <![CDATA[ */
window.onload = function(){
var pathToFlash = $('html').attr('MadCap:PathToHelpSystem') + 'Content/Resources/Code/ZeroClipboard.swf';
ZeroClipboard.setMoviePath(pathToFlash);
function bindToClipBord(element,content){
var clip = new ZeroClipboard.Client();
clip.setText(content);
clip.glue(element);
};
if(location.protocol==='file:'){
$('.copylink-marker').remove();
} else{
$('.copylink-marker').each(function(){
var text = $(this).parent().parent().children('.prettyprint').html();
$(this).hover(function(){
bindToClipBord(this,text);
},
function(){});
});
}
prettyPrint();
};
/* ]]> */</script>
<link href="../../../SkinSupport/MadCap.css" rel="stylesheet" />
<link href="../../../Resources/Stylesheets/OnlineStyle.css" rel="stylesheet" />
<script src="../../../Resources/Code/prettify.js">
</script>
<script src="../../../Resources/Code/lang-vb.js">
</script>
<script src="../../../Resources/Code/jquery.min.js">
</script>
<script src="../../../Resources/Code/ZeroClipboard.js">
</script>
<script src="../../../SkinSupport/MadCapAll.js" type="text/javascript">
</script>
</head>
<body>
<p class="MCWebHelpFramesetLink" style="display: none;"><a href="../../../../index_CSH.html#advanced_topics/refactoring_and_schema_evolution/refactoring_class_hierarchy/removing_class_from_a_hierarchy.htm" style="">Open topic with navigation</a>
</p>
<div class="MCBreadcrumbsBox"><span class="MCBreadcrumbsPrefix">You are here: </span><a class="MCBreadcrumbsLink" href="../../../advanced_topics.htm">Advanced Features</a><span class="MCBreadcrumbsDivider"> > </span><a class="MCBreadcrumbsLink" href="../../refactoring_and_schema_evolution.htm">Refactoring And Schema Evolution</a><span class="MCBreadcrumbsDivider"> > </span><a class="MCBreadcrumbsLink" href="../refactoring_class_hierarchy.htm">Refactoring Class Hierarchy</a><span class="MCBreadcrumbsDivider"> > </span><span class="MCBreadcrumbs">Removing Class From A Hierarchy</span>
</div>
<p>
<script type="text/javascript">/*<![CDATA[*/document.write('<a href="' + location.href +'">');
document.write("Direct Link");
document.write('</a>');/*]]>*/</script>
</p>
<p>
</p>
<h1><a name="kanchor94"></a>Removing Class From A Hierarchy</h1>
<p>In this example we have a Human class which inherits from the Primate class. Now we want to remove the Primate class and let the Human class inherit directly from the Mammal class.</p>
<p>
<img src="../remove-type-from-hierachy.png" />
</p>
<p>Unfortunately db4o doesn't support this kind of refactoring. We need to use a work-around. Basically we create a copy of the Human class with the new Inheritance-hierarchy and the copy the existing data over.</p>
<h2>Step by Step</h2>
<ol>
<li value="1">Create a copy of the Human class, for example HumanNew!</li>
<li value="2">Change the inheritance of the HumanNew-class to inherit directly from the Mammal-class.</li>
<li value="3">After that, load all existing Human-instances, copy the values over to HumanNew-instances. Store the HumanNew-instance and delete the old Human-instances</li>
</ol>
<p>Now the objects have the new inheritance hierarchy. You can delete the old Human-class.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IList<Human> allMammals = container.Query<Human>();
foreach (Human oldHuman in allMammals)
{
HumanNew newHuman = new HumanNew("");
newHuman.BodyTemperature = oldHuman.BodyTemperature;
newHuman.IQ = oldHuman.IQ;
newHuman.Name = oldHuman.Name;
container.Store(newHuman);
container.Delete(oldHuman);
}</pre>
<div class="codesnippet-meta">RemoveClassFromHierarchy.cs: copy the data from the old type to the new one
<div class="codedownload"><a href="../../../CodeExamples/strategies/refactoring/removehierarchy/Example-refactoring-removehierarchy-csharp.zip" class="codedownload" MadCap:conditions="Primary.Online">Download Code</a></div><div class="codedownload copylink-marker" MadCap:conditions="Primary.Online"><a href="#copy">Copy Code</a></div></div>
</div>
<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim allMammals As IList(Of Human) = container.Query(Of Human)()
For Each oldHuman As Human In allMammals
Dim newHuman As New HumanNew("")
newHuman.BodyTemperature = oldHuman.BodyTemperature
newHuman.IQ = oldHuman.IQ
newHuman.Name = oldHuman.Name
container.Store(newHuman)
container.Delete(oldHuman)</pre>
<div class="codesnippet-meta">RemoveClassFromHierarchy.vb: copy the data from the old type to the new one
<div class="codedownload"><a href="../../../CodeExamples/strategies/refactoring/removehierarchy/Example-refactoring-removehierarchy-vb.zip" class="codedownload" MadCap:conditions="Primary.Online">Download Code</a></div><div class="codedownload copylink-marker" MadCap:conditions="Primary.Online"><a href="#copy">Copy Code</a></div></div>
</div>
<p>Note that this example doesn't change existing references from the old instances to the new ones. You need to do this manually as well.</p>
<script type="text/javascript" src="../../../SkinSupport/MadCapBodyEnd.js">
</script>
</body>
</html>
