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POExtend DataTable in C#
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copied!<p>A static constructor for class <code>SourceManager</code> goes through all modules/classes and discovers all classes that implement <code>ISource</code>. It will instantiate each one of these and expose an <code>IEnumerable</code> of them as a static property called <code>IEnumerable<ISource> Sources</code>. For simplicity <code>ISource</code> has two properties, <code>DataTable Table { get; }</code> and <code>string UniqueName { get; }</code>. When instantiated each different <code>ISource</code> is responsible for populating its <code>Table</code> from SQL, MDX, etc. For all the <code>ISource</code>'s I've written thus far, loading the <code>Table</code> with all <code>DataRow</code>s when instantiated has been sufficient. However <strong>I now have a situation where I'd like to load the <code>Table</code> with <code>DataRow</code>'s lazily, rather than all up front. How do I do this?</strong> I will walk through an example. </p> <p><code>PermissionSource</code> implements <code>ISource</code>. Its <code>Table</code> property, that has a <code>private set</code> is given a value of <code>new PermissionDataTable()</code>. Its <code>UniqueName</code> is <code>"Permissions"</code>. As of right now there are no permissions loaded from the database into this <code>Table</code> property.</p> <pre><code>ISource permissionSource = SourceManager.Sources. Where(s => "Permission".Equals(s.UniqueName)).First(); </code></pre> <p>Now we've obtained the <code>PermissionSource</code>, but through an interface. Let's get a permission.</p> <pre><code>DataRow row = permissionSource.Table.Rows.Cast<DataRow>(). Where(r => r["PermissionName"].Equals("PermissionName")).First() </code></pre> <p>I've overriden the <code>Rows</code> property in <code>PermissionDataTable</code> so that the above, somehow, gets the value of the permissions associated with <code>"PermissionName"</code> in the database. Other permissions are not loaded.</p> <p>I don't have a choice in the permissions system and I don't have a choice to not use a <code>DataTable</code>.</p> <p><strong>EDIT:</strong></p> <p>In my example I would need to override the <code>Rows</code> property of <code>DataTable</code>. <code>Rows</code>, though, is a <a href="http://msdn.microsoft.com/en-us/library/system.data.datarowcollection.aspx" rel="noreferrer">DataRowCollection</a> which is <code>sealed</code>. Thus there isn't much that can be done in terms of creating a minimal custom DataTable implementation like I want to do.</p>

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