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/ParentingCollection.cs

@@ -0,0 +1,107 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.IO;
+using System.Reflection;
+
+namespace Nuclex.Support.Collections {
+
+  /// <summary>Collection that automatically assigns an owner to all its elements</summary>
+  /// <remarks>
+  ///   This collection automatically assigns a parent object to elements that
+  ///   are managed in it. The elements have to derive from the Parentable&lt;&gt;
+  ///   base class.
+  /// </remarks>
+  /// <typeparam name="ParentType">Type of the parent object to assign to items</typeparam>
+  /// <typeparam name="ItemType">Type of the items being managed in the collection</typeparam>
+  public class ParentingCollection<ParentType, ItemType> : Collection<ItemType>, IDisposable
+    where ItemType : Parentable<ParentType>
+    where ParentType : class {
+
+    /// <summary>Called when the object is garbage-collected</summary>
+    ~ParentingCollection() {
+      Dispose(false); // called from GC
+    }
+
+    /// <summary>Reparents all elements in the collection</summary>
+    /// <param name="parent">New parent to take ownership of the items</param>
+    internal void Reparent(ParentType parent) {
+      this.parent = parent;
+
+      for(int index = 0; index < Count; ++index)
+        base[index].SetParent(parent);
+    }
+
+    /// <summary>Called when the asset needs to release its resources</summary>
+    /// <param name="calledByUser">
+    ///   Whether the mehod has been called from user code. If this argument
+    ///   is false, the object is being disposed by the garbage collection and
+    ///   it mustn't access other objects (including the attempt to Dispose() them)
+    ///   as these might have already been destroyed by the GC.
+    /// </param>
+    protected virtual void Dispose(bool calledByUser) {
+
+      // Only destroy the other resources when we're not being called from
+      // the garbage collector, otherwise we'd risk accessing objects that
+      // have already been disposed
+      if(calledByUser) {
+
+        // Have the items do their cleanup work
+        Reparent(null);
+
+        // Dispose of all the items in the collection
+        foreach(ItemType item in this) {
+          IDisposable disposable = item as IDisposable;
+          if(disposable != null)
+            disposable.Dispose();
+        }
+
+        // Remove all items from the collection
+        base.ClearItems();
+
+      }
+
+    }
+
+    /// <summary>Clears all elements from the collection</summary>
+    protected override void ClearItems() {
+      for(int index = 0; index < Count; ++index)
+        base[index].SetParent(null);
+
+      base.ClearItems();
+    }
+
+    /// <summary>Inserts a new element into the collection</summary>
+    /// <param name="index">Index at which to insert the element</param>
+    /// <param name="item">Item to be inserted</param>
+    protected override void InsertItem(int index, ItemType item) {
+      base.InsertItem(index, item);
+      item.SetParent(this.parent);
+    }
+
+    /// <summary>Removes an element from the collection</summary>
+    /// <param name="index">Index of the element to remove</param>
+    protected override void RemoveItem(int index) {
+      base[index].SetParent(null);
+      base.RemoveItem(index);
+    }
+
+    /// <summary>Takes over a new element that is directly assigned</summary>
+    /// <param name="index">Index of the element that was assigned</param>
+    /// <param name="item">New item</param>
+    protected override void SetItem(int index, ItemType item) {
+      base.SetItem(index, item);
+      item.SetParent(this.parent);
+    }
+
+    /// <summary>Release all resources owned by the instance explicitely</summary>
+    void IDisposable.Dispose() {
+      Dispose(true); // Called by user
+    }
+
+    /// <summary>Parent this collection currently belongs to</summary>
+    private ParentType parent;
+
+  }
+
+} // namespace Nuclex.Support.Collections