Unable to Redirect To Main page after facebook login

FaceBookConnect.API_Key = "xxxxxxxxxx";
           FaceBookConnect.API_Secret = "xxxxxxxxxxxxxxxxxxxxxxx";



           if (!IsPostBack)
           {
               if (Request.Cookies["email"] != null)
               {
                   txtuser.Text = Request.Cookies["email"].Value;
                   txtpass.Attributes.Add("value", Request.Cookies["pass"].Value);
               }

               //FB Login
               if (Request.QueryString["error"] == "access_denied")
               {
                   ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('User has denied access.')", true);
                   return;
               }

               string code = Request.QueryString["code"];
               if (!string.IsNullOrEmpty(code))
               {
                   string data = FaceBookConnect.Fetch(code, "me");
                   FaceBookUser faceBookUser = new JavaScriptSerializer().Deserialize<FaceBookUser>(data);
                   DataSet chkdata = CommonMethods.SelectData("Select * from Register where email='" + faceBookUser.Email + "'");
                   if (chkdata.Tables[0].Rows.Count == 0)
                   {
                       cmd = new SqlCommand("insert into Register(email,pass,name,contactway,userview,type,cDate) values(@email,@pass,@name,@contactway,@userview,@type,Getdate())", cn);
                       cn.Open();
                       cmd.Parameters.AddWithValue("@email", faceBookUser.Email);
                       cmd.Parameters.AddWithValue("@pass", "Fblogin");
                       cmd.Parameters.AddWithValue("@name", faceBookUser.Name);
                       cmd.Parameters.AddWithValue("@contactway", "Visible Email Address");
                       cmd.Parameters.AddWithValue("@userview", "Yes");
                       cmd.Parameters.AddWithValue("@type", "Private Seller");
                       //cmd.Parameters.AddWithValue("@cdate", DateTime.Now.ToString());
                       cmd.ExecuteNonQuery();
                       cn.Close();
                   }
                   Session["email"] = faceBookUser.Email;
                   Session["username"] = faceBookUser.Name;
                   Label2.Text = faceBookUser.Email;
                   string url = "Main.aspx?email=" + Label2.Text + "";
                   bool a = true;
                   if (a == true)
                   {
                       HttpContext.Current.ApplicationInstance.CompleteRequest();
                       Response.Redirect(url, false);

                       //Response.Write(url);
                   }
               }
           }

I have tried all possible efforts and googled but din get any solution please anyone help me<br />
Thank you