Create a TreeView from a Database in Windows Forms and C#

Introduction

A TreeView control provides a way to display information in a hierarchical structure using nodes.

Root Node (Parent Node)

The top level nodes in a TreeView is called the Root nodes.

Child nodes

The root nodes (also known as parent nodes) can have nodes that can be viewed when they are expanded. These nodes are called child nodes. The user can expand a root node by clicking the plus sign (+) button.

Table Definitions

Parent Nodes

CREATE TABLE [dbo].[MNUPARENT](
               [MAINMNU] [varchar](20) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
               [STATUS] [varchar](1) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
               [MENUPARVAL] [int] IDENTITY(1,1) NOT NULL,
 CONSTRAINT [PK_MNUPARENT] PRIMARY KEY CLUSTERED
(
               [MENUPARVAL] ASC
)WITH (PAD_INDEX  = OFF, IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]

Insert Sample Hierarchical Data

SET IDENTITY_INSERT MNUPARENT ON
GO
INSERT INTO MNUPARENT(MAINMNU, STATUS, MENUPARVAL) VALUES('Finanace','Y',1)
INSERT INTO MNUPARENT(MAINMNU, STATUS, MENUPARVAL) VALUES('Inventory','Y',2)
GO
SET IDENTITY_INSERT MNUPARENT OFF
GO

Child Nodes

CREATE TABLE [dbo].[MNUSUBMENU](
               [MENUPARVAL] [int] NOT NULL,
               [FRM_CODE] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
               [FRM_NAME] [varchar](20) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
               [MNUSUBMENU] [int] NOT NULL,
               [STATUS] [varchar](1) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
PRIMARY KEY CLUSTERED
(
               [MNUSUBMENU] ASC
)WITH (PAD_INDEX  = OFF, IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
N [PRIMARY]

Sample Insert Statements

INSERT INTO MNUSUBMENU(MENUPARVAL,FRM_NAME,MNUSUBMENU,STATUS) VALUES(1,'Child Finance',10,'Y')
INSERT INTO MNUSUBMENU(MENUPARVAL,FRM_NAME,MNUSUBMENU,STATUS) VALUES(1,'Accounting',20,'Y')
INSERT INTO MNUSUBMENU(MENUPARVAL,FRM_NAME,MNUSUBMENU,STATUS) VALUES(20,'Audit',30,'Y')
INSERT INTO MNUSUBMENU(MENUPARVAL,FRM_NAME,MNUSUBMENU,STATUS) VALUES(30,'Acc. Standards',40,'Y')

Alternatively, you can have a single table to maintain this data of parent and child nodes.

Now let us start a new project and populate the TreeView.

1. Create a new project and name it LoadTreeView.
   
   

2. Set the form's Name Property to FrmTreeView and its Text Property to Populate TreeView.

3. Add a tree view control to the form and set its dock property to Left

4. To configure the connection settings of the Data Source add an application configuration File
   
   From Project -> "Add" -> "New Item..."
   
   

5. Paste the code below into the App.config File:

   <?xml version="1.0" encoding="utf-8" ?>
   <configuration>
     <connectionStrings>
       <add name ="ConnString" connectionString ="Data Source=yourServerName; User Id =yourUserName; Password =yourPwd;" providerName ="System.Data.SqlClient"/>
     </connectionStrings>
   </configuration>

6. To access the connection string from code add a reference to System.Configuration and add the namespace using System.Configuration.
   
   

7. In the form's Load Event paste the following code:

   String connectionString;
   connectionString = ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString;
   conn = new SqlConnection(connectionString);
   String Sequel = "SELECT MAINMNU,MENUPARVAL,STATUS FROM MNUPARENT";
   SqlDataAdapter da = new SqlDataAdapter(Sequel, conn);
   DataTable dt = new DataTable();
   conn.Open();
   da.Fill(dt);
   foreach (DataRow dr in dt.Rows)
   {
       parentNode = treeView1.Nodes.Add(dr["MAINMNU"].ToString());
       PopulateTreeView(Convert.ToInt32(dr["MENUPARVAL"].ToString()), parentNode);
   }
   treeView1.ExpandAll();
   

8. The Treeview is populated with its child nodes using the PopulateTreeView Method we have defined as in the following:

   private void PopulateTreeView(int parentId, TreeNode parentNode)
   {
       String Seqchildc = "SELECT MENUPARVAL,FRM_NAME,MNUSUBMENU FROM MNUSUBMENU WHERE MENUPARVAL=" + parentId + "";
       SqlDataAdapter dachildmnuc = new SqlDataAdapter(Seqchildc, conn);
       DataTable dtchildc = new DataTable();
       dachildmnuc.Fill(dtchildc);
       TreeNode childNode;
       foreach (DataRow dr in dtchildc.Rows)
       {
           if (parentNode == null)
               childNode = treeView1.Nodes.Add(dr["FRM_NAME"].ToString());
           else
               childNode = parentNode.Nodes.Add(dr["FRM_NAME"].ToString()); 
               PopulateTreeView(Convert.ToInt32(dr["MNUSUBMENU"].ToString()), childNode);
       }
   }

9. Build and run the program that results in the output shown in the following:
   
   

10. Add the following piece of code to the treeview Double-Click Event:

    private void treeView1_DoubleClick(object sender, EventArgs e)
    {
        MessageBox.Show(treeView1.SelectedNode.FullPath.ToString());
    }

11. When you double-click a node on the Treeview control a message is displayed with the fullpath to the node. Here I have clicked the Acc. Standards node.
    
    

Program

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Configuration;
using System.Data.SqlClient;
namespace LoadTreeView
{
    public partial class FrmTreeView : Form
    {
        SqlConnection conn;
        TreeNode parentNode = null;
        public FrmTreeView()
        {
            InitializeComponent();
        }
        private void FrmTreeView_Load(object sender, EventArgs e)
        {
            String connectionString;
            connectionString = ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString;
            conn = new SqlConnection(connectionString);
            String Sequel = "SELECT MAINMNU,MENUPARVAL,STATUS FROM MNUPARENT";
            SqlDataAdapter da = new SqlDataAdapter(Sequel, conn);
            DataTable dt = new DataTable();
            conn.Open();
            da.Fill(dt);
            foreach (DataRow dr in dt.Rows)
            {
                parentNode = treeView1.Nodes.Add(dr["MAINMNU"].ToString());
                PopulateTreeView(Convert.ToInt32(dr["MENUPARVAL"].ToString()), parentNode);
            }
            treeView1.ExpandAll();
        }
        private void PopulateTreeView(int parentId, TreeNode parentNode)
        {
            String Seqchildc = "SELECT MENUPARVAL,FRM_NAME,MNUSUBMENU FROM MNUSUBMENU WHERE MENUPARVAL=" + parentId + "";
            SqlDataAdapter dachildmnuc = new SqlDataAdapter(Seqchildc, conn);
            DataTable dtchildc = new DataTable();
            dachildmnuc.Fill(dtchildc);
            TreeNode childNode;
            foreach (DataRow dr in dtchildc.Rows)
            {
                if (parentNode == null)
                    childNode = treeView1.Nodes.Add(dr["FRM_NAME"].ToString());
                else
                    childNode = parentNode.Nodes.Add(dr["FRM_NAME"].ToString());
                PopulateTreeView(Convert.ToInt32(dr["MNUSUBMENU"].ToString()), childNode);
            }
        }
        private void treeView1_DoubleClick(object sender, EventArgs e)
        {
            MessageBox.Show(treeView1.SelectedNode.FullPath.ToString());
        }
    }
}

Conclusion

In this article, we have discussed how to populate a treeview dynamically in a C# application and display the entire path to the node on an event.