ASP.Net TreeView with Parent Child relationship from Database in ASP.Net

I cannot go on deep detail, but here's a TreeView you can use as reference

HTML

<h3>
    Vehicle Details</h3>
<hr />
<asp:TreeView ID="TreeView1" runat="server" ImageSet="XPFileExplorer" NodeIndent="15">
    <HoverNodeStyle Font-Underline="True" ForeColor="#6666AA" />
    <NodeStyle Font-Names="Tahoma" Font-Size="8pt" ForeColor="Black" HorizontalPadding="2px"
        NodeSpacing="0px" VerticalPadding="2px"></NodeStyle>
    <ParentNodeStyle Font-Bold="False" />
    <SelectedNodeStyle BackColor="#B5B5B5" Font-Underline="False" HorizontalPadding="0px"
        VerticalPadding="0px" />
</asp:TreeView>

Namespaces

using System.Data;
using System.Data.SqlClient;
using System.Configuration;

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        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(),
                Value = row["Id"].ToString()
        };
        if (parentId == 0)
        {
            TreeView1.Nodes.Add(child);
            DataTable dtChild = this.GetData("SELECT Id, Name FROM VehicleSubTypes WHERE VehicleTypeId = " + child.Value);
            PopulateTreeView(dtChild, int.Parse(child.Value), child);
        }
        else
        {
            treeNode.ChildNodes.Add(child);
        }
    }
}
private DataTable GetData(string query)
{
    DataTable dt = new DataTable();
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    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;
    }
}

SQL

CREATE TABLE [VehicleTypes](
	[Id] [int] NOT NULL,
	[Name] [varchar](50) NOT NULL,
 CONSTRAINT [PK_VehicleTypes] PRIMARY KEY CLUSTERED 
(
	[Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
-----------------

CREATE TABLE [VehicleSubTypes](
	[Id] [int] NOT NULL,
	[Name] [varchar](50) NOT NULL,
	[VehicleTypeId] [int] NOT NULL,
 CONSTRAINT [PK_VehicleSubTypes] PRIMARY KEY CLUSTERED 
(
	[Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

ALTER TABLE [dbo].[VehicleSubTypes]  WITH CHECK ADD  CONSTRAINT [FK_VehicleSubTypes_VehicleTypes] FOREIGN KEY([VehicleTypeId])
REFERENCES [dbo].[VehicleTypes] ([Id])
GO

ALTER TABLE [dbo].[VehicleSubTypes] CHECK CONSTRAINT [FK_VehicleSubTypes_VehicleTypes]
GO


-----------------------
INSERT INTO [VehicleTypes]
           ([Id]
           ,[Name])
     VALUES
           (1
           ,'Cars')
GO
INSERT INTO [VehicleTypes]
           ([Id]
           ,[Name])
     VALUES
           (2
           ,'Bikes')
GO
--------------------------
INSERT INTO [VehicleSubTypes]
           ([Id]
           ,[Name]
           ,[VehicleTypeId])
     VALUES
           (1
           , 'Alto'
           , 1)           
GO
INSERT INTO [VehicleSubTypes]
           ([Id]
           ,[Name]
           ,[VehicleTypeId])
     VALUES
           (2
           , 'WagonR'
           ,1)           
GO
INSERT INTO [VehicleSubTypes]
           ([Id]
           ,[Name]
           ,[VehicleTypeId])
     VALUES
           (3
           , 'Scorpio'
           , 1)           
GO
INSERT INTO [VehicleSubTypes]
           ([Id]
           ,[Name]
           ,[VehicleTypeId])
     VALUES
           (4
           , 'Duster'
           ,1)           
GO
INSERT INTO [VehicleSubTypes]
           ([Id]
           ,[Name]
           ,[VehicleTypeId])
     VALUES
           (5
           , 'Discover'
           ,2)           
GO
INSERT INTO [VehicleSubTypes]
           ([Id]
           ,[Name]
           ,[VehicleTypeId])
     VALUES
           (6
           , 'Avenger'
           ,2)           
GO
INSERT INTO [VehicleSubTypes]
           ([Id]
           ,[Name]
           ,[VehicleTypeId])
     VALUES
           (7
           , 'Unicorn'
           ,2)           
GO
INSERT INTO [VehicleSubTypes]
           ([Id]
           ,[Name]
           ,[VehicleTypeId])
     VALUES
           (8
           , 'Karizma'
           ,2)           
GO

Screenshots