在c#代码隐藏中设置和检索cookie

我试图在SelectedIndexChanged事件中将下拉列表的选择保存到cookie中。

protected void BranchNumberList_SelectedIndexchanged(object sender, EventArgs e)
{
   HttpCookie myCookie = new HttpCookie("default_Loc", BranchNumberList.SelectedValue);
   myCookie.Expires = DateTime.Now.AddDays(365);
   Response.Cookies.Add(myCookie);
   ViewDate.Enabled = true;
   SelectEverything();
}

myCookie看起来不错，我可以在带有快速监视的响应对象中看到它。

当从Page_Load调用此方法时，我尝试在下次登录时检索它。

private void BranchName()
{
   DatabaseHelpers dh = new DatabaseHelpers();
   DataSet DrpDownSrc = dh.FillBranchSelection(objConn);
   BranchNumberList.DataSource = DrpDownSrc;
   BranchNumberList.DataTextField = "BranchName";
   BranchNumberList.DataValueField = "LocationID";
   BranchNumberList.DataBind();
   BranchNumberList.Items.Insert(0, "Select a branch");
   try
   {
      BranchNumberList.SelectedValue = this.Request.Cookies["default_Loc"].Value;
   }
   catch (Exception)
   {
      BranchNumberList.SelectedIndex = 0;
   }
}

我总是得到'this.Request.Cookies["default_Loc"]'为null。

有人看到我哪里出错了吗？