树形控件TreeView与数据库绑定

数据库
create database TreeView
go
use Treeview

create table node1
(
nd1id int primary key,
nd1name varchar(32)
)

create table node2
(
nd2id int primary key,
nd1id int,
nd2name varchar(32)
)

create table node3
(
nd3id int primary key,
nd2id int,
nd3name varchar(32)
)

insert node1 values(0,'node1_1')
insert node1 values(1,'node1_2')
insert node1 values(2,'node1_3')
insert node1 values(3,'node1_4')
insert node2 values(0,0,'node2_1')
insert node2 values(1,0,'node2_2')
insert node2 values(2,1,'node2_3')
insert node2 values(3,1,'node2_4')
insert node2 values(4,2,'node2_5')
insert node2 values(5,3,'node2_6')
insert node2 values(6,2,'node2_7')

insert node3 values(0,0,'node3_1')
insert node3 values(1,0,'node3_2')
insert node3 values(2,1,'node3_3')
insert node3 values(3,2,'node3_4')
insert node3 values(4,1,'node3_5')
insert node3 values(5,3,'node3_6')
insert node3 values(6,5,'node3_7')
insert node3 values(7,6,'node3_8')
insert node3 values(8,3,'node3_9')
insert node3 values(9,4,'node3_10')
insert node3 values(10,5,'node3_11')

VS代码

void PopulateCategories(TreeNode node)
     {
         string sql = "Select nd1name, nd1id From node1";
         DataSet resultSet;
         resultSet = Getdataset(sql, null);
         if (resultSet.Tables.Count > 0)
         {
             foreach (DataRow row in resultSet.Tables[0].Rows)
             {
                 TreeNode NewNode = new TreeNode(row["nd1name"].ToString(), row["nd1id"].ToString());
                 NewNode.PopulateOnDemand = true;
                 NewNode.SelectAction = TreeNodeSelectAction.Expand;
                 node.ChildNodes.Add(NewNode);
             }
         }
     }

     void PopulateProducts(TreeNode node)
     {

         string sql = "Select nd2name,nd2id From node2 " + " Where nd1id = @id";
         SqlParameter para = new SqlParameter("@id", SqlDbType.Int);
         para.Value = node.Value;
         //sqlQuery.Parameters.Add("@id", SqlDbType.Int).Value = node.Value;
         DataSet ResultSet = Getdataset(sql, para);
         if (ResultSet.Tables.Count > 0)
         {
             foreach (DataRow row in ResultSet.Tables[0].Rows)
             {
                 TreeNode NewNode = new TreeNode(row["nd2name"].ToString(), row["nd2id"].ToString());
                 NewNode.PopulateOnDemand = true;
                 NewNode.SelectAction = TreeNodeSelectAction.Expand;
                 node.ChildNodes.Add(NewNode);
             }
         }
     }

     void PopulateProducts1(TreeNode node)
     {

         string sql = "Select nd3name,nd3id From node3 " + " Where nd2id = @id";
         SqlParameter para = new SqlParameter("@id", SqlDbType.Int);
         para.Value = node.Value;
         //sqlQuery.Parameters.Add("@id", SqlDbType.Int).Value = node.Value;
         DataSet ResultSet = Getdataset(sql, para);
         if (ResultSet.Tables.Count > 0)
         {
             foreach (DataRow row in ResultSet.Tables[0].Rows)
             {
                 TreeNode NewNode = new TreeNode(row["nd3name"].ToString(), row["nd3id"].ToString());
                 NewNode.PopulateOnDemand = false;
                 NewNode.SelectAction = TreeNodeSelectAction.SelectExpand;
                 node.ChildNodes.Add(NewNode);
             }
         }
     }

     private DataSet Getdataset(string sql,SqlParameter paralist)
     {
         string strconn = "database=treeview;server=.;Integrated Security=SSPI";
         SqlConnection conn = new SqlConnection(strconn);
         SqlCommand cmd = new SqlCommand();
         if (paralist != null)
         {

             cmd.Parameters.Add(paralist);
            
         }
         cmd.CommandText = sql;
         cmd.Connection = conn;
         SqlDataAdapter da = new SqlDataAdapter(cmd);
         DataSet ds = new DataSet();
         da.Fill(ds);
         return ds;
     }

     protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
     {
         if (e.Node.ChildNodes.Count == 0)
         {
             switch (e.Node.Depth)
             {
                 case 0:
                     PopulateCategories(e.Node);
                     break;
                 case 1:
                     PopulateProducts(e.Node);
                     break;
                 case 2:
                     PopulateProducts1(e.Node);
                     break;
                
                  
             }
         }
     }

     protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
     {
         Response.Write("adfdf");

     }
     protected void TreeView1_TreeNodeExpanded(object sender, TreeNodeEventArgs e)
     {
         //Response.Write("adfdf");
     }