求一个遍历DataTable的算法

Question

如下DataTable，其中有Id列、父Id列和内容Item列,具体数据如下：Id    Pid    Item
1      0      A
2      1      B
3      1      C
4      2      D
5      2      E
6      3      F
7      3      G
8      3      H请问如何通过遍历以上DataTable得到下面形式的字符串?A>B>D;A>B>E;A>C>F;A>C>G;A>C>H下面是DataTable对应的树型结构：            A
         /     \
       B         C
     /  \     /  |  \
    D    E   F   G   H

Answer 1

 class PlayNode
    {
        public int ID;
        public int PID;
        public string NAME;
        public PlayNode(int _ID, int _PID, string _NAME)
        {
            this.ID = _ID;
            this.PID = _PID;
            this.NAME = _NAME;
        }
    }
    public class Play
    {
        SortedDictionary<int, PlayNode> Lst = new SortedDictionary<int, PlayNode>();
        
                void ReadNode()
        {
            Lst.Clear();
            string sqlData = "SELECT * FROM PLAY order by id";
            DataTable dtDate = DataSQL.Select(sqlData);
            if (dtDate != null)
            {
                for (int i = 0; i < dtDate.Rows.Count; i++)
                {
                    Lst.Add(int.Parse(dtDate.Rows[i]["ID"].ToString().Trim()),new PlayNode(int.Parse(dtDate.Rows[i]["ID"].ToString().Trim()),int.Parse(dtDate.Rows[i]["PID"].ToString().Trim()),dtDate.Rows[i]["NAME"].ToString().Trim()));
                }
            }            
        }        public string Display()
        {
            string Outstr = "";
            ReadNode();
            if (Lst.Count != 0)
            {
                string sqlData = "SELECT * FROM PLAY  where pid in (2,3) order by id";
                DataTable dtDate = DataSQL.Select(sqlData);
                if (dtDate != null)
                {
                    for (int i = 0; i < dtDate.Rows.Count; i++)
                    {
                       Outstr +=DG(int.Parse(dtDate.Rows[i]["PID"].ToString().Trim()), dtDate.Rows[i]["NAME"].ToString().Trim(), Lst)+"；";
                    }
                }            
            }
            return Outstr;
        }        string DG(int PID, string LastStr, SortedDictionary<int, PlayNode> Dict)
        {
            if (PID != 0)
            {
                int TmpID = PID;
                string TmpLast = LastStr;
                foreach (KeyValuePair<int, PlayNode> KP in Dict)
                {
                    if (PID == KP.Key)
                    {
                        TmpLast = KP.Value.NAME + ">"+TmpLast;
                        TmpID = KP.Value.PID ;
                        break;
                    }
                }
                return DG(TmpID, TmpLast, Dict);               
            }
            else return LastStr;
        }
    }直接调用Display()方法即可

Answer 2

递归
    public void CreateTree(int parentID, TreeNode node, DataTable dt, TreeView treeView)  
    {  
        //实例化一个DataView dt = 传入的DataTable   
        dv = new DataView(dt);  
        //筛选(相当于select * from tabMenu where menuParentID = 传入的 parentID)   
        dv.RowFilter = "[menuParentID]=" + parentID;  
  
        //用foreach遍历dv   
        foreach (DataRowView row in dv)  
        {  
            //第一次加载时为空   
            if (node == null)  
            {  
                //创建根节点   
                TreeNode root = new TreeNode();  
                //必须与数据库的对应   
                root.Text = row["menuName"].ToString();  
                root.Value = row["menuID"].ToString();  
                //添加根节点   
                this.TreeView1.Nodes.Add(root);  
                //递归调用方法本身   
                CreateTree(int.Parse(row["menuID"].ToString()), root, dt, treeView);  
  
            }  
            else  
            {  
                //添加子节点   
                TreeNode childNode = new TreeNode();  
                childNode.Text = row["menuName"].ToString();  
                childNode.Value = row["menuID"].ToString();  
                node.ChildNodes.Add(childNode);  
                CreateTree(int.Parse(row["menuID"].ToString()), childNode, dt, treeView);  
  
            }  
        }  
  
    }  
}
类似

Answer 3

错误 1 当前上下文中不存在名称“DataSQL”

Answer 4

与绑定TreeView有类似之处，但绑定TreeView是添加子节点，父节点只会出现一次；而现在问题在于，有多少个子节点，父节点就会出现多少次。

Answer 5

换了下思路，终于还是实现了。/// <summary>
        /// 根据DataTable中的数据得到特定规则的字符串
        /// </summary>
        /// <param name="dt">DataTable对象</param>
        /// <returns>特定规则的字符串</returns>
        public static string GetString(DataTable dt)
        {
            string strList = string.Empty;
            //先对DataTable表中的数据进行整理
            ManageDataTable(dt);            //对DataTable按Id进行升序排列
            DataView dv = new DataView(dt);
            dv.Sort = "Id";
            dt = dv.ToTable();            //循环调用递归方法组合专利分类字符串
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                strList += dt.Rows[i]["Item"].ToString();
                GetString(ref strList, dt, i);
                dt.Rows.RemoveAt(i);//移除组合后的项
                i--;//循环变量相应减1
                strList += "；";
            }            return strList;
        }        /// <summary>
        /// 整理DataTable表中的数据(使父分类的数量等于子分类之和)
        /// </summary>
        /// <param name="dt">DataTable对象</param>
        private static void ManageDataTable(DataTable dt)
        {
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                int pIdCount = 1;
                int idCount = 0;                for (int j = i + 1; j < dt.Rows.Count; j++)
                {
                    if (dt.Rows[i]["Pid"].ToString() == dt.Rows[j]["Pid"].ToString())
                    {
                        pIdCount++;
                    }                    if (dt.Rows[i]["Pid"].ToString() == dt.Rows[j]["Id"].ToString())
                    {
                        idCount++;
                    }
                }                if (pIdCount <= idCount)
                {
                    continue;
                }                for (int l = 0; l < dt.Rows.Count; l++)
                {
                    if (dt.Rows[i]["Pid"].ToString() == dt.Rows[l]["Id"].ToString())
                    {
                        for (int k = 0; k < pIdCount - idCount; k++)
                        {
                            DataRow dr = dt.Rows[l];
                            dt.ImportRow(dr);//重复添加
                        }                        i += pIdCount - 1;
                        break;
                    }
                }
            }
        }        /// <summary>
        /// 递归组合字符串
        /// </summary>
        /// <param name="categoryList">初始字符串</param>
        /// <param name="dt">DataTable对象</param>
        /// <param name="rowIndex">初始行号</param>
        private static void GetString(ref string categoryList, DataTable dt, int rowIndex)
        {
            for (int i = rowIndex + 1; i < dt.Rows.Count; i++)
            {
                if (dt.Rows[rowIndex]["Id"].ToString() == dt.Rows[i]["Pid"].ToString())
                {
                    categoryList += "〉" + dt.Rows[i]["Item"].ToString();
                    GetString(ref categoryList, dt, i);//递归调用自身
                    dt.Rows.RemoveAt(i);//移除组合后的项
                    i--;//循环变量相应减1
                    break;
                }
            }
        }