how to sort Datatable data that is displayed in Gridview

protected void btnSubmit_Click(object sender, EventArgs e)
{
    string s="select * from items";
    SqlDataAdapter da = new SqlDataAdapter(s,con);
    DataTable dt = new DataTable();
    da.Fill(dt);
    Session["a"]=dt;
    Response.Redirect("Default2.aspx");
}

protected void Page_Load(object sender, EventArgs e)
{
   DataTable dt=(DataTable)Session["a"];
   GridView1.DataSource = dt;
   GridView1.DataBind();
}