จะทำ Update ข้อมูลค่ะแต่ทำยังงัยก็ไม่ได้ซักที ช่วยทีค่ะ

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;
using System.Text;
using System.Linq;

public partial class Garage3 : System.Web.UI.Page
{
    //static string strConn = ConnectionString.ConnectCar;
    //SqlConnection Conn = new SqlConnection(strConn);
    //StringBuilder sb = new StringBuilder();

    //bool status = false;

    protected void Page_Load(object sender, EventArgs e)
    {

        string GarageID = "";
        DBCarDataContext dbCar = new DBCarDataContext();
        HttpCookie Data = new HttpCookie("Data");
        GarageID = Request.QueryString["GarageID"];
        if (GarageID!=""&&GarageID!=null)
        {
            Data.Values["GarageID"] = GarageID.ToString();
            var garage = dbCar.tbl_Garages.Where(g => g.Garage_ID == GarageID.ToInt()).FirstOrDefault();
            lblGarageID.Text = garage.Garage_ID.ToString();
            lblGarageName.Text = garage.Garage_Name;
            txtG_Add.Text = garage.Garage_Add;
            txtG_District.Text = garage.Garage_District;
            txtG_Fax.Text = garage.Garage_Fax;
            txtG_SubDistrict.Text = garage.Garage_SubDistrict;
            txtG_Tel.Text = garage.Garage_Phone;
            txtG_Zip.Text = garage.Garage_Postcode;
            txtMobile.Text = garage.Garage_CellPhone;
            ddlG_Province.Text = garage.Garage_Province;
        }
        Response.Cookies.Add(Data);
    }

    protected void cmdUpdate_Click(object sender, EventArgs e)
    {
        HttpCookie cook = Request.Cookies["Data"];
        if (cook == null)
        {
            return;
        }

        //DBCarDataContext dbCar = new DBCarDataContext();

        int GarageID = lblGarageID.Text.ToInt();
        //string GarageName = cook.Values["GarageName"].ToString();
        DBCarDataContext db = new DBCarDataContext();
        var GarageEdit = db.tbl_Garages.Where(c => c.Garage_ID == GarageID).FirstOrDefault();

        //if (GarageEdit != null)
        //{
        GarageEdit.Garage_Add = txtG_Add.Text;
        GarageEdit.Garage_SubDistrict = txtG_SubDistrict.Text;
        GarageEdit.Garage_District = txtG_District.Text;
        GarageEdit.Garage_CellPhone = txtMobile.Text;
        GarageEdit.Garage_Fax = txtG_Fax.Text;
        GarageEdit.Garage_Phone = txtG_Tel.Text;
        GarageEdit.Garage_Postcode = txtG_Zip.Text;
        GarageEdit.Garage_Province = ddlG_Province.Text;
        
        db.SubmitChanges();

        //}
       
    }
}