TreeView控件保存恢复结点展开状态

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Web;
using  System.Web.UI.WebControls;

///   <summary>
///  Heros TreeView保存和恢复结点展开状态的辅助类
///   </summary>
public   class  TreeNodesExpandStateManager : IDisposable
{
    TreeView _tree;
    List < TreeNode >  nodes  =   new  List < TreeNode > ();

     public   static   string  SessionKey  =   " TreeNodesExpandState " ;
     public  TreeNodesExpandStateManager(TreeView tree)
    {
        _tree  =  tree;
    }

     ///   <summary>
     ///  保存当前树的展开状态
     ///   </summary>
     public   void  SaveExpandState()
    {
         foreach  (TreeNode node  in   this ._tree.Nodes)
        {
            SearchExpandedNode(node);
        }
    }

     private   void  SearchExpandedNode(TreeNode node)
    {
         if  (node  ==   null )
             return ;
         else
        {
             if  (node.Expanded  ??   false )
            {
                nodes.Add(node);
                 foreach  (TreeNode item  in  node.ChildNodes)
                {
                    SearchExpandedNode(item);
                }
            }
        }
    }

     ///   <summary>
     ///  恢复当前树的展开状态
     ///   </summary>
     public   void  RestoreExpandState()
    {
         foreach  (TreeNode node  in   this ._tree.Nodes)
        {
            SetNodeExpandState(node);
        }
    }

     ///   <summary>
     ///  用于跨页操作时，恢复到指定树
     ///   </summary>
     ///   <param name="tree"></param>
     public   void  RestoreExpandStateToTree(TreeView tree)
    {
         foreach  (TreeNode node  in  tree.Nodes)
        {
            SetNodeExpandState(node);
        }
    }

     private   void  SetNodeExpandState(TreeNode node)
    {
         if  (node  ==   null )
             return ;
         else
        {
             if  ( this .nodes.Contains(node,  new  EqualEntity()))
            {
                node.Expand();
                 foreach  (TreeNode item  in  node.ChildNodes)
                {
                    SetNodeExpandState(item);
                }
            }
        }
    }

     ///   <summary>
     ///  将指定树展开状态存入会话，一般在树的展开和合闭事件中调用
     ///   </summary>
     ///   <param name="tree"> 目标树 </param>
     public   static   void  SaveExpandStateInSession(TreeView tree,  string  sessionKey)
    {
         if  (tree  ==   null )
             return ;
        TreeNodesExpandStateManager manager  =   new  TreeNodesExpandStateManager(tree);
        manager.SaveExpandState();
        HttpContext.Current.Session[sessionKey]  =  manager;
    }

     ///   <summary>
     ///  将指定树展开状态存入默认会话，一般在树的展开和合闭事件中调用
     ///   </summary>
     ///   <param name="tree"> 目标树 </param>
     public   static   void  SaveExpandStateInSession(TreeView tree)
    {
        SaveExpandStateInSession(tree, SessionKey);
    }

     ///   <summary>
     ///  将Session中的结点展开状态恢复到指定树，在树结点添加结束后调用
     ///   </summary>
     ///   <param name="tree"> 目标树 </param>
     public   static   void  RestoreExpandStateToTreeFromSession(TreeView tree,  string  sessionKey)
    {
         if  (HttpContext.Current.Session[sessionKey]  ==   null   ||  tree  ==   null )
             return ;
        TreeNodesExpandStateManager manager  =  HttpContext.Current.Session[sessionKey]  as  TreeNodesExpandStateManager;
        manager.RestoreExpandStateToTree(tree);
    }
     ///   <summary>
     ///  将默认Session中的结点展开状态恢复到指定树，在树结点添加结束后调用
     ///   </summary>
     ///   <param name="tree"> 目标树 </param>
     public   static   void  RestoreExpandStateToTreeFromSession(TreeView tree)
    {
        RestoreExpandStateToTreeFromSession(tree, SessionKey);
    }

     #region  IDisposable 成员

     public   void  Dispose()
    {
         this .nodes.Clear();
         this .nodes  =   null ;
         this ._tree.Dispose();
    }

     #endregion

      ~ TreeNodesExpandStateManager()
    {
         this .Dispose();
    }

      public   class  EqualEntity : IEqualityComparer < TreeNode >
     {
          #region  IEqualityComparer<TreeNode> 成员

          public   bool  Equals(TreeNode x, TreeNode y)
         {
              if  (x  ==   null   ||  y  ==   null )
                  return   false ;
              return  x.Value.Equals(y.Value);
         }

          public   int  GetHashCode(TreeNode obj)
         {
              return  obj.GetHashCode();
         }

          #endregion
     }
}