1using System;
  2using System.Data;
  3using OnLineExam.DataAccessLayer;
  4
  5namespace OnLineExam.CommonComponent
  6...{
  7    /**//// <summary>
  8    /// 一个通用的树状菜单类
  9    /// </summary>
 10    public class Tree
 11    ...{
 12        private string _treeHtml;
 13        private DataTable _dataTable;
 14
 15        /**//// <summary>
 16        /// 根据DataTable对象，生成一棵树
 17        /// </summary>
 18        /// <param name="dataTable">树中节点的数据</param>
 19        /// <returns>树的HTML代码</returns>
 20        public string CreateTree(DataTable dataTable)
 21        ...{
 22            this._dataTable = dataTable;
 23            this.CreateSubTree(0);
 24            return _treeHtml;
 25        }
 26
 27        /**//// <summary>
 28        /// 获取父节点编号为parentId的所有节点，并用DataTable返回
 29        /// </summary>
 30        /// <param name="parentId">父节点编号</param>
 31        /// <returns>DataTable形式的所有孩子节点数据</returns>
 32        private DataTable GetChilds(int parentId)
 33        ...{
 34            DataTable childNodes = new DataTable();
 35            childNodes = this._dataTable.Clone();
 36
 37            foreach (DataRow dr in this._dataTable.Rows)
 38            ...{
 39                if (Convert.ToInt32(dr["ParentId"]) == parentId)
 40                ...{
 41                    childNodes.ImportRow(dr);
 42                }
 43            }
 44
 45            return childNodes;
 46        }
 47
 48        /**//// <summary>
 49        /// 判断编号为nodeId的节点是否为叶子节点
 50        /// </summary>
 51        /// <param name="nodeId">待判断的节点编号</param>
 52        /// <returns>是叶子节点：返回true；否则：返回false</returns>
 53        private bool IsLeaf(int nodeId)
 54        ...{
 55            foreach (DataRow dr in this._dataTable.Rows)
 56                if (Convert.ToInt32(dr["ParentId"]) == nodeId)
 57                    return false;
 58            return true;
 59        }
 60
 61        /**//// <summary>
 62        /// 得到编号为nodeId的节点的父节点编号
 63        /// </summary>
 64        /// <param name="nodeId">节点编号</param>
 65        /// <returns>父节点编号</returns>
 66        private int GetParent(int nodeId)
 67        ...{
 68            foreach (DataRow dr in this._dataTable.Rows)
 69                if (Convert.ToInt32(dr["NodeId"]) == nodeId)
 70                    return Convert.ToInt32(dr["ParentId"]);
 71            return -1;
 72
 73        }
 74
 75        /**//// <summary>
 76        /// 得到编号为nodeId的节点的级别，根节点为0
 77        /// </summary>
 78        /// <param name="nodeId">待计算的巨额电编号</param>
 79        /// <returns>节点的级别，根节点为0</returns>
 80        private int GetLevel(int nodeId)
 81        ...{
 82            int parentId = GetParent(nodeId);
 83            if (parentId == 0) return 1;
 84            else
 85                return GetLevel(parentId) + 1;    //递归
 86        }
 87
 88        /**//// <summary>
 89        /// 递归生成根编号为nodeId的树
 90        /// </summary>
 91        /// <param name="nodeId">所要生成子树的根节点</param>
 92        private void CreateSubTree(int nodeId)
 93        ...{
 94            DataTable childNodes = this.GetChilds(nodeId);    //获取根节点的所有孩子
 95
 96            //循环生成根节点的所有孩子对应的HTML
 97            int childId = 0;
 98            foreach (DataRow dr in childNodes.Rows)
 99            ...{
100                childId = Convert.ToInt32(dr["nodeId"]);
101                this._treeHtml += "<div id=div_" + childId.ToString() + ">";
102
103                //根据该孩子的级别，生成一些空格，以体现层次结构
104                for (int i = 0; i < GetLevel(childId); i++)
105                    this._treeHtml += "&nbsp;&nbsp;&nbsp;&nbsp;";
106
107                //如果该孩子是叶子节点，则生成其HTML代码
108                if (this.IsLeaf(childId))
109                ...{
110                    this._treeHtml += "<img src='..\\Images\\folder.gif'/><a href=" + dr["Url"] + ">" + dr["Text"] + "</a></div>";
111                }
112                //如果该孩子为中间节点，则首先构造其HTML，然后递归生成其所有孩子的HTML
113                else
114                ...{
115                    this._treeHtml += "<img src='..\\Images\\folderopen.gif'/><a href=" + dr["Url"] + ">" + dr["Text"] + "</a></div>";
116                    this.CreateSubTree(childId);//递归
117                }
118            }
119        }
120    }
121}