Getting an error "index was outside the bounds of the array" in C#

try
        {
            bool check = ValidStudent(TBRNo.Text);

//after executing above statement program jumps up to the catch block n raise d exception

            if (check == false)
            {
                SqlDataReader dr = FetchDetails_frmString(TBRNo.Text);
                DataTable dt = new DataTable();
                
                dt.Load(dr);
                Session["dr"] = dr;
                Session["FetchDetails_frmString"] = dt;
                con.Close();
                if (dt.Rows.Count > 0)
                {
                    string ip = GetIpAddress();
                    int i = StoreIpAddress(ip, TBRNo.Text);
                    if (i > 0)
                    {
                        ClientScript.RegisterStartupScript(GetType(), "Onload", "alert('Login Successful!')", true);
                        Response.Redirect("~/Student/home.aspx");
                    }
                    else
                    { 
                        
                    }
                   
                }
                else
                {
                    ClientScript.RegisterStartupScript(GetType(), "Onload", "alert('Access Denied.....This string does not exist')", true);
                }
            }
           else
            {
                ClientScript.RegisterStartupScript(GetType(), "Onload", "alert('You have Already login this Website')", true);
            }
        }
        catch (Exception o)
        {
            Label8.Text = o.Message;
            ClientScript.RegisterStartupScript(GetType(), "Onload", "alert('Access Denied.....Some Problem occured')", true);
        }
        finally 
        { 
            con.Close();         
        }