动态加载树

   对于http://www.dojochina.com/?q=node/578对ExtJs动态加载树，现在给出.net版本。首先数据库结构表一样。这里我用的是sqlserver 2000 DDL如下：

   if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[FK_LoadTree_LoadTree]') and OBJECTPROPERTY(id, N'IsForeignKey') = 1)
ALTER TABLE [dbo].[LoadTree] DROP CONSTRAINT FK_LoadTree_LoadTree
GO

if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[LoadTree]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [dbo].[LoadTree]
GO

CREATE TABLE [dbo].[LoadTree] (
 [ItemID] [int] NOT NULL ,
 [ItemName] [varchar] (20) COLLATE Chinese_PRC_CI_AS NULL ,
 [ParentID] [int] NOT NULL ,
 [IsAvailable] [int] NULL
) ON [PRIMARY]
GO

 

  在Ext中 Tree.AsyncTreeNode实现对树结点的异步加载。此时我们只需让服务端生成指定格式的Json字符串（格式可参看Ext的例子）。js代码依然是惯例，这里我还是把他贴出来。

Ext.onReady( function ()
{
    var Tree=Ext.tree;
    var tree = new Tree.TreePanel( {

            el : 'tree-div',//目标div容器

            autoScroll : true,

            animate : true,

            enableDD : true,

            containerScroll : true,

            loader : new Tree.TreeLoader( {

                  dataUrl : 'TreeJsonData.aspx '// 动态载入数据的请求地址

            })

      });

      var root = new Tree.AsyncTreeNode( {

            text : '教考分离系统',

            draggable : false,

            id : '-1'//这是post给服务端的。一般为root的id
      });

      tree.setRootNode(root);

      tree.render();

      root.expand();
      // root.expandChildNodes();


});

 

   下面就是服务端的事。个人认为可以用sql语句递归查处。再生成json应该会更简单，但我sql还没写出来。所以我是先全部读到datatable中，在datatable中进行的各种处理。下面为服务端完整代码：

 

public partial class TreeJsonData : System.Web.UI.Page
{
   //StringBuilder strTreeJson = new StringBuilder();
    protected void Page_Load(object sender, EventArgs e)
    {
        try
        {
            //throw new Exception();
            int rootid = int.Parse(Request.Form["node"]);
            DataTable dt = DBHelper.GetAllTree();
            // string treeJson = JSONHelper.ToJSON(dt, dt.Rows.Count, null);
            // Response.Write(treeJson);
            //  Response.Write("["+GetNodeString(dt, -1)+"]");
            Response.Write(GetSigleNodeString(dt, rootid));
        }
        catch
        {
            Response.Write("[{ id:100,text :\" Sorry! 没有任何节点\",leaf:true }]");
        }
    }

    /**//// <summary>
    /// 得到适合Ext.Tree.TreeLoader的json字符串（包含根结点）适合有多个根结点的情况
    /// </summary>
    /// <param name="dt">包含了所有树形结构数据的DataTable</param>
    /// <param name="parentid">开始往下搜索的id</param>
    /// <returns>json</returns>

    private string GetNodeString(DataTable dt, int parentid)
    {
        DataRow[] drs = dt.Select("ItemId = " + parentid.ToString());
        StringBuilder strTreeJson = new StringBuilder(); 
        if (drs.Equals(null))
        {
            //return "[{ id:" + parentid.ToString() + ",text : 没有任何节点,leaf:true }]";
            return null;
        }
        else
        {
            foreach (DataRow dr in drs)
            {
                string  tempid=dr["ItemId"].ToString();
                strTreeJson.Append("{ ");
                strTreeJson.Append(" id :\'" +tempid + "\', text : \'" + dr["ItemName"].ToString()+"\',");
                ArrayList arr = null;
                if (HasChild(dt, tempid,out arr))
                {
                    strTreeJson.Append("children : [");
                    for (int i = 0; i < arr.Count; i++)
                    {
                        if (i == arr.Count - 1)
                        {
                            strTreeJson.Append(GetNodeString(dt, int.Parse(arr[i].ToString())));
                        }
                        else
                        {
                            strTreeJson.Append(GetNodeString(dt, int.Parse(arr[i].ToString())));
                            strTreeJson.Append(",");
                        }
                      
                    }
               
                    strTreeJson.Append("]");
                    strTreeJson.Append("}"); 
                }
                else
                {
                    strTreeJson.Append("leaf : true }");
                }
               // strTreeJson.Append(",");
            }
        }

      
        return strTreeJson.ToString();

    }
    /**//// <summary>
    /// 得到适合Ext.Tree.TreeLoader的json字符串适合有单个根结点的情况
    /// </summary>
    /// <param name="dt"></param>
    /// <param name="parentId"></param>
    /// <returns></returns>
    private string GetSigleNodeString(DataTable dt, int parentId)
    {
        DataRow[] singledr = dt.Select("ItemId = " + parentId.ToString());
        StringBuilder singleTreeJson= new StringBuilder(); 
        if (singledr.Length > 1)
        {
            throw new Exception("给定parentId包含多个结点请使用GetNodeString()方法");
        }
        else if (singledr.Equals(null))
        {
            return null;

        }
        else
        {
            DataRow[] dr = dt.Select("ParentId = " + parentId.ToString()+ "and ParentId<>ItemId");
            singleTreeJson.Append("[");

            for (int i = 0; i < dr.Length; i++)
            {   int j=int.Parse(dr[i]["ItemId"].ToString());
                if (i == dr.Length - 1)
                {
                    singleTreeJson.Append(GetNodeString(dt, j));
                }
                else
                {
                    singleTreeJson.Append(GetNodeString(dt, j));
                    singleTreeJson.Append(",");
                }
            }
            singleTreeJson.Append("]");
            return singleTreeJson.ToString();
        }

 
    }
    /**//// <summary>
    /// 给定id判断是否含有子节点及输出的包含所有子节点的id的ArrayList
    /// </summary>
    /// <param name="dt"></param>
    /// <param name="id"></param>
    /// <param name="childid"></param>
    /// <returns></returns>
    private bool HasChild(DataTable dt, string id,out ArrayList childid)
    {
       DataRow[]  dr= dt.Select("ParentId =" +id +"and ItemId<>ParentId " );
       childid = new ArrayList();
       if (dr.Length == 0)
       {
          
           childid = null;
           return false;
       }
       else
       {
         
           for (int i = 0; i < dr.Length; i++)
           {
               childid.Add(dr[i]["ItemId"]);
           }
           return true;
       }
    }
 
}

 

  看看效果，呵呵！！！Ok