Imported newly created Nuclex.Support library which contains various supporting classes not related to a specific topic

git-svn-id: file:///srv/devel/repo-conversion/nusu@1 d2e56fa2-650e-0410-a79f-9358c0239efd

Source/Collections/Parentable.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+
+namespace Nuclex.Support.Collections {
+
+  /// <summary>Base class for objects that can be parented to an owner</summary>
+  /// <typeparam name="ParentType">Type of the parent object</typeparam>
+  public class Parentable<ParentType>
+    where ParentType : class {
+
+    /// <summary>Assigns a new parent to this instance</summary>
+    internal void SetParent(ParentType parent) {
+      ParentType oldParent = this.parent;
+      this.parent = parent;
+
+      OnParentChanged(oldParent);
+    }
+
+    /// <summary>The parent object that owns this instance</summary>
+    protected ParentType Parent {
+      get { return this.parent; }
+    }
+
+    /// <summary>Invoked whenever the instance's owner changes</summary>
+    /// <remarks>
+    ///   When items are parented for the first time, the oldParent argument will
+    ///   be null. Also, if the element is removed from the collection, the
+    ///   current parent will be null.
+    /// </remarks>
+    /// <param name="oldParent">Previous owner of the instance</param>
+    protected virtual void OnParentChanged(ParentType oldParent) { }
+
+    /// <summary>Current parent of this object</summary>
+    private ParentType parent;
+
+  }
+
+} // namespace Nuclex.Support.Collections