How to convert code from asp.net web forms to razor asp.net core page

Question

I need to fill tree view with parent child on razor asp.net core but I don't know how to fill tree view parent child 

and child can select checkbox and can see related chid for every parent 

my code with web form csharp

protected void Page_Load(object sender, EventArgs e)
{

if (!IsPostBack)
{
FillModuleName();
}
}
private void FillModuleName()
{
    string sql = "";
    clsDB obj = new clsDB(Session["g_ConnectionString"].ToString());
    DataSet ds = new DataSet();
    DataSet ds1 = new DataSet();
    int i = 0;
    try
    {
        sql = "select * from tblWebModule where parentmenucode='00'";
        ds = obj.ExecuteQuery(sql);
        if (ds.Tables[0].Rows.Count > 0)
        {
            foreach (DataRow dr in ds.Tables[0].Rows)
            {
                TreeNode TN = new TreeNode();
                TN.Text = dr["MenuName"].ToString();
                TN.Value = dr["ChildMenuCode"].ToString();
                sql = "select * from tblWebModule where parentmenucode='" + dr["ChildMenuCode"].ToString() + "'";
                ds1 = obj.ExecuteQuery(sql);
                foreach (DataRow rw in ds1.Tables[0].Rows)
                {
                    TreeNode CN = new TreeNode();
                    CN.Text = rw["MenuName"].ToString();
                    CN.Value = rw["ChildMenuCode"].ToString();
                    TN.ChildNodes.Add(CN);
                }
                tvModules.Nodes.Add(TN);
            }
        }
    }
    catch (Exception ex)
    {

    }
}

on html tree view as below
    <tr>
                <td align="left" style="width: 100px; height: 24px">
                </td>
                <td align="left" style="width: 500px; height: 24px">
                    <asp:TreeView ID="tvModules" runat="server" ShowCheckBoxes="All" Font-Names="Verdana" Font-Size="Small" ImageSet="BulletedList">
                    </asp:TreeView>
                </td>
                <td align="left" style="width: 100px; height: 24px">
                </td>
            </tr>
            <tr>

so please How to organize this code on razor page model as below 

page model

public void OnGet()

{

How to load tree view parent and child

}

on treeview.cs.html

{

layout

}

How to link page model with html to load tree view

<asp:TreeView ID="tvModules" runat="server" ShowCheckBoxes="All" Font-Names="Verdana" Font-Size="Small" ImageSet="BulletedList">
                    </asp:TreeView>

sample for result expected