treeview（樹加載）

數據庫結構

    id：int類型，主鍵，自增列；

    Name：char類型；

    paraid：int類型

 

窗台拖入控件treeview。

 

1.版本1

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace _1.多級菜單
{
    public partial class Form1 : Form
    {
        //獲取鏈接
        string ConnString = System.Configuration.ConfigurationManager.ConnectionStrings["ConnSring"].ToString();
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.LoadData(null);
        }
        /// <summary>
        /// 載入tn的所有子節點，如果tn=null,說明是跟節點
        /// </summary>
        /// <param name="tn"></param>
        private void LoadData(TreeNode tn)
        {
            if (tn == null)
            {
                //為空說明是根節點,添加節點時直接在控件的Nodes屬性上添加就行了
                using (SqlConnection conn = new SqlConnection(ConnString))
                {
                    //查找根節點 所以parenti=0
                    string sql = "select * from Table_Tree where parentid=0";
                    using (SqlCommand cmd = new SqlCommand(sql, conn))
                    {
                        conn.Open();
                        using (SqlDataReader dr = cmd.ExecuteReader())
                        {
                            while (dr.Read())
                            {
                                TreeNode cNode = new TreeNode();
                                cNode.Text = dr["name"].ToString();
                                 cNode.Tag = dr["Id"];//tag沒有意義，不被現實出來，所以就存儲id
                                 treeView1.Nodes.Add(cNode);//節點加到treeview
                                LoadData(cNode);

                            }
                        }
                    }
                }

            }
            else
            {
                //參數tn!=null  那就是說要找tn的所有子節點,並做為tn的子節點.怎么在tn這個節點上添加子節點呢?  tn.Nodes.Add(cNode);
                using (SqlConnection conn = new SqlConnection(ConnString))
                {
                    //查找根節點 所以parenti=0
                    string sql = "select * from Table_Tree where parentid=@id";
                    using (SqlCommand cmd = new SqlCommand(sql, conn))
                    {
                        cmd.Parameters.AddWithValue("@Id", tn.Tag);//tn是TreeNode對象
                        conn.Open();
                        using (SqlDataReader dr = cmd.ExecuteReader())
                        {
                          
                            while (dr.Read())
                            {
                                TreeNode cNode = new TreeNode();
                                cNode.Text = dr["name"].ToString();
                                cNode.Tag = dr["Id"];//tag沒有意義，不被現實出來，所以就存儲id
                                tn.Nodes.Add(cNode);
                                LoadData(cNode);

                            }
                        }
                    }
                }


            }
        }
    }
}
運行結果：

2.版本2（數據庫相同）

 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace _02Tree
{
    public partial class Form1 : Form
    {
        string ConnString = System.Configuration.ConfigurationManager.ConnectionStrings["ConnString"].ToString();
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.LoadData(null);
        }
        /// <summary>
        /// 載入tn的所有子節點,如果tn=null,說明載的是根節點
        /// </summary>
        private void LoadData(TreeNode tn)
        {
            //獲得要添加的節點
            List<TblTree> addNodes = this.GetNodesByParentId(tn == null ? 0 : Convert.ToInt32(tn.Tag));

            foreach (var oneNode in addNodes)
            {
                TreeNode ctNode = new TreeNode();
                ctNode.Text = oneNode.Name;
                ctNode.Tag = oneNode.Id;
                if (tn == null)
                {
                    //如果是要節點,添加到控件上
                    treeView1.Nodes.Add(ctNode);
                }
                else
                {
                    //如果tn不為null,說明要為tn添加子節點,所以我們就添加到tn上
                    tn.Nodes.Add(ctNode);
                }
                this.LoadData(ctNode);//調用自己,為ctNode添加子節點                
            }
        }
        private List<TblTree> GetNodesByParentId(int parentId)
        {
            List<TblTree> allNodes = new List<TblTree>();
           
            string sql = "select * from Table_Tree where parentid=@id"; 
            SqlDataReader dr = CommonCode.Sqlhelper.ExecuteReader(sql, new SqlParameter("@id", parentId));
            while (dr.Read())
            {
                TblTree oneNode = new TblTree();
                oneNode.Name = dr["name"].ToString();
                oneNode.Id = Convert.ToInt32(dr["id"]);
                oneNode.Parentid = parentId;
                allNodes.Add(oneNode);
            }
            dr.Close();
            return allNodes;
        }   
    }
}
運行效果圖：

 還有TblTree類：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace _02Tree
{
    public class TblTree
    {
        int id;

        public int Id
        {
            get { return id; }
            set { id = value; }
        }
        string name;

        public string Name
        {
            get { return name; }
            set { name = value; }
        }
        int parentid;

        public int Parentid
        {
            get { return parentid; }
            set { parentid = value; }
        }


    }
}
數據庫通用公共類：版本1和版本2通用

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;

namespace CommonCode
{
    public static class Sqlhelper
    {
        private static readonly string ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString;
        //執行數據庫無非就是執行cmd的以下方法
        //1. ExecuteNonQuery 執行一個insert update delete
        public static int ExecuteNonQuery(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(ConnectionString))
            {
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddRange(parameters);
                    conn.Open();
                    return cmd.ExecuteNonQuery();
                }
            }

        }
        //2.ExecuteScaler 返回結果集的第一行第一列
        public static object ExecuteScaler(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(ConnectionString))
            {
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddRange(parameters);
                    conn.Open();
                    return cmd.ExecuteScalar();
                }
            }
        }

        //3.ExecuteReader 返回一個Reader對象,用於讀於多行多列數據
        //在數據庫上產生一個結果集,每次Read,從數據庫服務器上讀取一條數據回來,所以使用Reader讀取數據,不能與數據庫斷開連接.
        public static SqlDataReader ExecuteReader(string sql, params SqlParameter[] parameters)
        {
            SqlConnection conn = new SqlConnection(ConnectionString);
            
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddRange(parameters);
                    conn.Open();
                    try
                    {
                        //在sqlhelper中,由於dr在返回給用戶使用,所以注意dr不要使用using(){]
                        SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                        
                            return dr;
                        
                    }
                    catch (Exception ex)
                    {
                        conn.Close();
                        throw ex;
                       
                    }
          
                }
            }

        

        //4.執行一個sql語句,並把結果集放入本地的DataTable中.這里數據已
        //經放到本地,斷開數據庫連接,還是可以訪問到數據的.
        public static DataTable ExecuteDataTable(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(ConnectionString))
            {
                using (SqlDataAdapter da = new SqlDataAdapter(sql, conn))
                {
                    da.SelectCommand.Parameters.AddRange(parameters);
                    DataTable dt = new DataTable();
                    //Fill方法其實執行的是da.SelectCommand中的sql語句,這里可以寫conn.open也可以不寫,如果不寫,da會自動連接數據庫
                    da.Fill(dt);
                    return dt;
                }
            }
        }
    }
}