While working with treeview you can bind it with fixed items or with the dynamic items using the database data .

HTML for Treeview

<h3>
    Vehicle Details</h3>
<hr />


/* Defining treeview and its properties*/


<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>

Code Behind for Treeview

protected void PageLoad(object sender, EventArgs e)

 {

/*To load data from the table*/

 if (!this.IsPostBack) 

{ 


DataTable dt = this.GetData("SELECT Id, Name FROM VehicleTypes"); 


this.PopulateTreeView(dt, 0, null); 

}

 }


/* Aligning the data into parent child relationship*/

 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;

 } 


}