TreeView

WINFORM界面如下：


本文用了2张表,结构如下：
表province: province_id    province_name
表city:         city_id    city_name   province_id

完整代码如下：

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

namespace  test
{
     public  partial  class  TreeStruc : Form
    {
         public  TreeStruc()
        {
            InitializeComponent();
        }

        SqlConnection conn  =   new  SqlConnection( " server=zhuzy;integrated security=sspi;database=library " );
        SqlDataAdapter da;
        DataSet ds = new  DataSet();
        SqlCommand cmd;
         ///   <summary>
         ///  自定义节点类，继承于系统的 TreeNode 类，给节点增加一个 IsFirstExpand 属性
         ///   </summary>
         public   class  InheritTreeNode : TreeNode
        {
             private   bool  isFirstExpand  =   true ;

             public   bool  IsFirstExpand  // 属性
            {
                 get  {  return  isFirstExpand; }
                 set  { isFirstExpand  =  value; }
            }

             public  InheritTreeNode() :  base () { }
             public  InheritTreeNode( string  text) :  base (text) { }
        }

         string  id  =   "" ;
         private   void  TreeStruc_Load( object  sender, EventArgs e)
        {            
            da  =   new  SqlDataAdapter( " select province_id,province_name from province " , conn);
            da.Fill(ds,  " province " );
             for  ( int  i  =   0 ; i  <  ds.Tables[ " province " ].Rows.Count; i ++ )
            {
                InheritTreeNode root  =   new  InheritTreeNode(ds.Tables[ " province " ].Rows[i][ 1 ].ToString().Trim());
                id  =  ds.Tables[ " province " ].Rows[i][ 0 ].ToString().Trim();
                 this .treeView1.Nodes.Add(root);
                ReadChileNode(root);
                id  =   "" ; //
            }
             this .treeView1.SelectedNode  =  treeView1.Nodes[ 0 ];
        }

         ///   <summary>
         ///  读取 node 的子节点
         ///   </summary>
         private   void  ReadChileNode(TreeNode node)
        {
            da  =   new  SqlDataAdapter( " select city_name from city where province_id=' "   +  id  +   " ' " , conn);
            da.Fill(ds,  " city " );
             try
            {
                 for  ( int  j  =   0 ; j  <  ds.Tables[ " city " ].Rows.Count; j ++ )
                {
                    node.Nodes.Add( new  InheritTreeNode(ds.Tables[ " city " ].Rows[j][ 0 ].ToString().Trim()));
                }
            }
             catch  (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            ds.Tables[ " city " ].Clear(); //
        }

         ///   <summary>
         ///  节点展开之前事件
         ///   </summary>
         private   void  treeView1_BeforeExpand( object  sender, TreeViewCancelEventArgs e)
        {
            InheritTreeNode node  =  (InheritTreeNode)e.Node; // 获取要选中、展开、折叠或选择的树节点e.Node

             if  (node  !=   null )
            {
                 //  判断该节点是否首次被展开
                 if  (node.IsFirstExpand)
                {
                     for  ( int  i  =   0 ; i  <  node.Nodes.Count; i ++ )
                    {
                        ReadChileNode(node.Nodes[i]);  // 为 e.Node 下的每个子节点，添加子节点
                    }
                }
            }
            node.IsFirstExpand  =   false ;
        }
        
         ///   <summary>
         ///  将文本框输入的内容添加为父节点
         ///   </summary>
         private   void  btnAddParentNode_Click( object  sender, EventArgs e)
        {
             try
            {
                 string  strParentNode  =   this .textBox1.Text.ToString().Trim();
                da  =   new  SqlDataAdapter( " select province_name from province where province_name=' "   +  strParentNode  +   " ' " , conn);
                da.Fill(ds,  " province_name " );
                 int  nCount  =  ds.Tables[ " province_name " ].Rows.Count;
                 if  (textBox1.Text.ToString().Trim()  !=   "" )
                {
                     if  (nCount  ==   0 )  // 判断是否存在重复省份
                    {
                        da  =   new  SqlDataAdapter( " select max(province_id) from province " , conn);
                        da.Fill(ds,  " id " );

                         string  _max_province_id  =  ds.Tables[ " id " ].Rows[ 0 ][ 0 ].ToString().Trim();
                         int  nID  =  Convert.ToInt32(_max_province_id)  +   1 ;
                         string  strID  =   " 00 "   +  nID.ToString().Trim();

                         string  _insertSQL  =   " insert into province values(' "   +  strID  +   " ',' "   +  strParentNode  +   " ') " ;
                        cmd  =   new  SqlCommand(_insertSQL, conn);
                        conn.Open();
                        cmd.ExecuteNonQuery();
                        conn.Close();

                         this .treeView1.Nodes.Add(strParentNode);  // 使新增的节点在TreeView里显示
                        textBox1.Clear();
                        textBox1.Focus();
                    }
                     else
                    {
                        MessageBox.Show( " 当前新增的省份已经存在,请重新输入! " ,  " 提示 " , MessageBoxButtons.OK, MessageBoxIcon.Information);
                        textBox1.Clear();
                        textBox1.Focus();
                    }
                }
            }
             catch  (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

         ///   <summary>
         ///  在选择了父节点后，将文本框中的内容添加为其子节点
         ///   </summary>
         string  str_insert_province_id  =   "" ;
         string  str_insert_city_id  =   "" ;
         private   void  btnAddChildNode_Click( object  sender, EventArgs e)
        {
             try
            {
                TreeNode node  =   this .treeView1.SelectedNode;
                 string  strProvinceName  =  node.Text;
                 if  (node  !=   null )
                {
                    retunParentNode_ID(strProvinceName);
                    insertChildNode(node);
                    textBox1.Clear();
                    textBox1.Focus();
                }
                 else
                {
                    MessageBox.Show( " 请先选择需要新增城市信息的省份! " ,  " 提示 " , MessageBoxButtons.OK, MessageBoxIcon.Information);
                    textBox1.Clear();
                    textBox1.Focus();
                }
            }
             catch  (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
       }

         ///   <summary>
         ///  返回当前选择的父节点的province_id
         ///   </summary>
         ///   <returns></returns>
         private   string  retunParentNode_ID( string  strName)
        {
            da  =   new  SqlDataAdapter( " select province_id from province where province_name=' "   +  strName  +   " ' " , conn);
            da.Fill(ds,  " province_id " );
            str_insert_province_id  =  ds.Tables[ " province_id " ].Rows[ 0 ][ 0 ].ToString().Trim(); // 即将新增的子节点的province_id
             return  str_insert_province_id;
        }
         ///   <summary>
         ///  在当前选择的父节点下新增子节点
         ///   </summary>
         private   void  insertChildNode(TreeNode CurrentParentNode)
        {
             string  strChildNode  =   this .textBox1.Text.ToString().Trim();
             try
            {
                 if  (textBox1.Text.ToString().Trim()  !=   "" )
                {
                     string  strsql  =   " select * from city where province_id=' "   +  str_insert_province_id  +   " ' " ;
                    da  =   new  SqlDataAdapter(strsql, conn);
                    da.Fill(ds,  " tb " );
                     int  nCount1  =  ds.Tables[ " tb " ].Rows.Count;
                     if  (nCount1  ==   0 )  // 父节点下没有子节点
                    {
                         string  _city_id  =   " 0 "   +   " 1 " ;
                         string  _insertSQL  =   " insert into city values(' "   +  _city_id  +   " ',' "   +  strChildNode  +   " ',' "   +  str_insert_province_id  +   " ') " ;

                        cmd  =   new  SqlCommand(_insertSQL, conn);
                        conn.Open();
                        cmd.ExecuteNonQuery();
                        conn.Close();

                        CurrentParentNode.Nodes.Add(strChildNode);
                        textBox1.Clear();
                        textBox1.Focus();
                    }
                     if  (nCount1  !=   0 )  // 父节点下有子节点
                    {
                        da  =   new  SqlDataAdapter( " select city_name from city where city_name=' "   +  strChildNode  +   " ' " , conn);
                        da.Fill(ds,  " city_name " );
                         int  nCount2  =  ds.Tables[ " city_name " ].Rows.Count;
                         if  (nCount2  ==   0 )  // 不存在相同的子节点
                        {
                             string  _max_city_id  =   " select max(city_id) from city where province_id=' "   +  str_insert_province_id  +   " ' " ;
                            da  =   new  SqlDataAdapter(_max_city_id, conn);
                            da.Fill(ds,  " city_id " );
                            str_insert_city_id  =  ds.Tables[ " city_id " ].Rows[ 0 ][ 0 ].ToString().Trim();
                             int  nID  =  Convert.ToInt32(str_insert_city_id)  +   1 ;
                            str_insert_city_id  =   " 0 "   +  nID.ToString().Trim();

                             string  _insertSQL  =   " insert into city values(' "   +  str_insert_city_id  +   " ',' "   +  strChildNode  +   " ',' "   +  str_insert_province_id  +   " ') " ;

                            cmd  =   new  SqlCommand(_insertSQL, conn);
                            conn.Open();
                            cmd.ExecuteNonQuery();
                            conn.Close();

                            CurrentParentNode.Nodes.Add(strChildNode);
                            textBox1.Clear();
                            textBox1.Focus();
                        }
                         if  (nCount2  !=   0 )  // 存在相同的子节点
                        {
                            MessageBox.Show( " 已经存在此城市,请重新输入! " ,  " 提示 " , MessageBoxButtons.OK, MessageBoxIcon.Information);
                            textBox1.Clear();
                            textBox1.Focus();
                        }
                    }
                }
            }
             catch  (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}

备注：此树只实现2层结构