i am getting Exception as System.IndexOutOfRangeException/ or no rows at this position

if this happening i want to move on next row of table and if row is there that row's value should display

public partial class WebForm9 : System.Web.UI.Page
    {
       
        SqlCommand cmd = new SqlCommand();
        DataTable dt = new DataTable();
        DataRow drr;
       public string ans_tea;
        public string ans_stu;
        SqlConnection con = new SqlConnection(@"Data Source=.\sqlexpress;Initial Catalog=swatidb;Integrated Security=True;Pooling=False");
         static int i = 0;
        public void Page_Load(object sender, EventArgs e)
        {
           con.Open();
            string tea_id = TextBox2.Text;
            string s1 = "select student_id from Student where user_name='" + Session["sid"] + "'";
            SqlCommand cmd = new SqlCommand(s1, con);
        SqlDataReader dr;
            dr = cmd.ExecuteReader();
            if (dr.Read())
            {
                Label4.Text = dr[0].ToString();
                dr.Close();
            }
    }
      public void Button2_Click(object sender, System.EventArgs e)
        {
            string tea_id = TextBox2.Text;
            cmd = new SqlCommand("SELECT * from Question WHERE Teacher_id=@tea_id", con);
            
            cmd.Parameters.AddWithValue("@tea_id", tea_id);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
         da.Fill(dt);//at this line getting Exception so how can i avoid getting this Exception
            drr = dt.Rows[i];
             if (i == (dt.Rows.Count - 1))
            {
                Response.Write("Last record !");
            }
            else
            {
               i++;
             
            }
              Label3.Text = Convert.ToString(drr[0]);//for displaying question_id
                Label2.Text = Convert.ToString(drr[2]);//for displaying question
            con.Close();
       }