how to add multiple user control in asp.net

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protected void gv_SelectedIndexChanging(object sender, GridViewSelectEventArgs e)
{
ph.Controls.Add(LoadControl("WebUserControl.ascx"));
Session["i"] = Convert.ToInt32(Session["i"]) + 1;
}

protected void Page_Init(object sender, EventArgs e)
{
for (int i = 0; i < Convert.ToInt32(Session["i"]); i++)
{
ph.Controls.Add(LoadControl("WebUserControl.ascx"));
}
}