In this article I will explain with an example, how to populate TreeView from Database in Windows Forms (WinForms) Application using C# and VB.Net.
This article will illustrate how to use Recursion i.e. recursively call the same function to add Parent and Child Nodes to the TreeView control.
Database
In order to populate TreeView with Parent Child relationship, I have made use of two tables namely VehicleTypes and VehicleSubTypes. The schema and the data present in both the tables are as follows.
VehicleTypes
![Populate TreeView from Database in Windows Forms using C# and VB.Net]()
![Populate TreeView from Database in Windows Forms using C# and VB.Net]()
VehicleSubTypes
![Populate TreeView from Database in Windows Forms using C# and VB.Net]()
![Populate TreeView from Database in Windows Forms using C# and VB.Net]()
Note: You can download the database table SQL by clicking the download link below.
Form Design
The Form consists of a TreeView control.
![Populate TreeView from Database in Windows Forms using C# and VB.Net]()
Namespaces
You will need to import the following namespaces.
C#
using System.Data;
using System.Data.SqlClient;
VB.Net
Imports System.Data
Imports System.Data.SqlClient
Populating TreeView from database
The PopulateTreeView method is a recursive function. Inside the Form Load event, the TreeView is populated with the records from the VehicleTypes table.
Inside the PopulateTreeView method, a loop is executed over the DataTable and if the ParentId is 0 i.e. the node is a parent node, a query is executed over the VehicleSubTypes table to populate the corresponding child nodes and again the PopulateTreeView method is called.
This process continues until all parent nodes along with their child nodes are added to the TreeView.
C#
private void Form1_Load(object sender, EventArgs e)
{
DataTable dt = this.GetData("SELECT Id, Name FROM VehicleTypes");
this.PopulateTreeView(dt, 0, null);
}
private void PopulateTreeView(DataTable dtParent, int parentId, TreeNode treeNode)
{
foreach (DataRow row in dtParent.Rows)
{
TreeNode child = new TreeNode
{
Text = row["Name"].ToString(),
Tag = row["Id"]
};
if (parentId == 0)
{
treeView1.Nodes.Add(child);
DataTable dtChild = this.GetData("SELECT Id, Name FROM VehicleSubTypes WHERE VehicleTypeId = " + child.Tag);
PopulateTreeView(dtChild, Convert.ToInt32(child.Tag), child);
}
else
{
treeNode.Nodes.Add(child);
}
}
}
private DataTable GetData(string query)
{
DataTable dt = new DataTable();
string constr = @"Data Source=.\SQL2014;Initial Catalog=AjaxSamples;Integrated Security=true";
using (SqlConnection con = new SqlConnection(constr))
{
using (SqlCommand cmd = new SqlCommand(query))
{
using (SqlDataAdapter sda = new SqlDataAdapter())
{
cmd.CommandType = CommandType.Text;
cmd.Connection = con;
sda.SelectCommand = cmd;
sda.Fill(dt);
}
}
return dt;
}
}
VB.Net
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
Dim dt As DataTable = Me.GetData("SELECT Id, Name FROM VehicleTypes")
Me.PopulateTreeView(dt, 0, Nothing)
End Sub
Private Sub PopulateTreeView(dtParent As DataTable, parentId As Integer, treeNode As TreeNode)
For Each row As DataRow In dtParent.Rows
Dim child As New TreeNode() With { _
.Text = row("Name").ToString(), _
.Tag = row("Id") _
}
If parentId = 0 Then
TreeView1.Nodes.Add(child)
Dim dtChild As DataTable = Me.GetData("SELECT Id, Name FROM VehicleSubTypes WHERE VehicleTypeId = " & child.Tag)
PopulateTreeView(dtChild, Convert.ToInt32(child.Tag), child)
Else
treeNode.Nodes.Add(child)
End If
Next
End Sub
Private Function GetData(query As String) As DataTable
Dim dt As New DataTable()
Dim constr As String = "Data Source=.\SQL2014;Initial Catalog=AjaxSamples;Integrated Security=true"
Using con As New SqlConnection(constr)
Using cmd As New SqlCommand(query)
Using sda As New SqlDataAdapter()
cmd.CommandType = CommandType.Text
cmd.Connection = con
sda.SelectCommand = cmd
sda.Fill(dt)
End Using
End Using
Return dt
End Using
End Function
Screenshot
![Populate TreeView from Database in Windows Forms using C# and VB.Net]()
Downloads
