Полезные Скрипты Oracle - Заполнение данных Data Bound TreeView в C#

Visual Studio 2008 offers some out-of-the-box features that we can easily create a Treeview control in the form designer without writing much code. However if we need to (Most of time I believe we do) programmatically populate a Treeview menu, particularly if we want to populate a Treeview based on a database table, this does require some codes. In this demo, I am demonstrating how we can populate a Treeview control with database tables. The backend database is Oracle 10g R2,

I use the employee table under HR schema. It shouldn’t matter which database you are using, as long as your table or view in hierarchy structure, for instance like:

ID EMP_NAME PARENT_ID
100 Steven
101 Neena 100
102 Lex 100
103 Alexander 102
104 Bruce 103
105 David 103
106 Valli 103
107 Diana 103
108 Nancy 101

- Firstly in the form designer, we drag a Treeview control and make it dock left.
- Drag a Splitter control to the right hand side of the form and make it dock left as shown below.

- Drag a Panel control to the right hand side and make it dock top.
- Drag a Splitter control to the bottom right and make it dock top.
- Drag a third Panel to the bottom right and make it fill the rest of the screen as shown below.

- To populate the TreeViewNode, I am using a recursive function. The tag property is used to store the level of the hierarchy.

namespace TreeViewDemo
{
public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        DataSet dsTreeView = new DataSet();

        // Populate public DataSet
        private DataSet PopulateDataTable()
        {
            string connectionString = "Data Source=orcl;Persist Security Info=True; "
                + "User ID=hr;Password=hr;Unicode=True";

            string queryString = "select * from employees";

            OracleConnection connection = new OracleConnection(connectionString);
            OracleCommand command = new OracleCommand(queryString, connection);
            OracleDataAdapter da = new OracleDataAdapter(command);

            try
            {
                connection.Open();
                if (!dsTreeView.Tables.Contains("emp"))
                    dsTreeView.Tables.Add("emp");
                da.Fill(dsTreeView, "emp");
            }
            catch (OracleException oex)
            {
                throw new Exception(oex.Message);
            }
            finally
            {
                connection.Close();
            }
            return dsTreeView;
        }

        // The level of tree
        int intLevel = 0;

        // Recursive function to populate Treeview node
        public void FillChildren(TreeNode _Parent, int _ParentID)
        {
            intLevel++;
            DataView Data = new DataView(dsTreeView.Tables["emp"]);
            Data.RowFilter = "manager_id = " + _ParentID;

            // Define the image index in the lowest level
            if (Data.Count == 0)
            {
                _Parent.ImageIndex = 2;
                _Parent.SelectedImageIndex = 2;
            }

            foreach (System.Data.DataRowView foo in Data)
            {
                TreeNode t = BuildNode((string)foo["last_name"]);
                t.Tag = intLevel;
                FillChildren(t, int.Parse(foo["employee_id"].ToString()));
                _Parent.Nodes.Add(t);
                System.Diagnostics.Trace.WriteLine("Added node at level " + intLevel.ToString());
            }
            intLevel--;
        }

        private TreeNode BuildNode(string Text)
        {
            return new TreeNode(Text);
        }

        private void LoadMenuTreeView()
        {
            PopulateDataTable();
            DataView Data = new DataView(dsTreeView.Tables["emp"]);
            Data.RowFilter = "manager_id is null ";
            foreach (System.Data.DataRowView foo in Data)
            {
                TreeNode t = BuildNode((string)foo["last_name"]);
                t.Tag = 0;
                FillChildren(t, int.Parse(foo["employee_id"].ToString()));
                this.treeView1.Nodes.Add(t);
            }

            this.treeView1.ImageList = this.imageList1;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            LoadMenuTreeView();
        }

        private void treeView1_AfterExpand(object sender, TreeViewEventArgs e)
        {
            e.Node.ImageIndex = 1;
        }

        private void treeView1_AfterCollapse(object sender, TreeViewEventArgs e)
        {
            e.Node.ImageIndex = 0;
}
    }
}

Populate a Data Bound TreeView in .Net using C#