传值问题

  //展示数据
        public void ShowData(int id)//id值是通过传值过来的
        {
            S_model = B_S.Getdatabyid(id);
            if (S_model != null)
            {
                ViewState["Sid"] = S_model.ToString();//存储整个对象
                this.txtguest_company.Text = S_model.SERVER_ID.ToString();
                this.txtguest_linkman.Text = S_model.GUEST_LINKMAN.ToString();
                this.txtserver_Approve.Text = S_model.SERVER_APPROVE.ToString();
                this.txtserver_create.Text = S_model.SERVER_CREATE.ToString();
                this.txtserver_ispast.Text = S_model.SERVER_ISPAST.ToString();
                this.txtserver_name.Text = S_model.SERVER_NAME.ToString();
                this.txtserver_time.Text = S_model.SERVER_TIME.ToString();
                this.txtuser_name.Text = S_model.USER_NAME.ToString();
                this.txttypeid.Text = S_model.TYPE_ID.ToString();
                this.txtservertheme.Text = S_model.SERVER_THEME.ToString();
                this.txtservercontent.Text = S_model.SERVER_CONTENT.ToString();
                this.txtserverid.Text = S_model.SERVER_ID.ToString();
            }
           // Response.Write("哼");        }以上是根据id传值进来，获取值，在这里我用viewstate接受，然后根据这个获取值，在执行修改操作，上面的成功了，但修改时，却获取不到值，为什么呢？
修改代码如下：//修改
        protected void lbtnmodify_Click(object sender, EventArgs e)
        {
            CRM_MODEL.CRM_SERVER S_model = ViewState["id"] as CRM_MODEL.CRM_SERVER;
            if (S_model != null)
            {
                Response.Write("dhfs");//执行了显示的内容，为什么在哪里获得值，再重新操作，会得不到那个值呢？？？？？郁闷？？？？？？？
                S_model.SERVER_ID = Convert.ToInt32(this.txtserverid.Text);
                S_model.SERVER_THEME = this.txtservertheme.Text.Trim();
                S_model.SERVER_TIME = Convert.ToDateTime(this.txtserver_time.Text.Trim());
                S_model.SERVER_NAME = this.txtserver_name.Text.Trim();
                S_model.SERVER_ISPAST = Convert.ToBoolean(this.txtserver_ispast.Text.Trim());
                S_model.SERVER_CREATE = this.txtserver_create.Text.Trim();
                S_model.SERVER_CONTENT = this.txtservercontent.Text;
                S_model.SERVER_APPROVE = this.txttypeid.Text;
                S_model.GUEST_LINKMAN = this.txtguest_linkman.Text.Trim();
                S_model.GUEST_COMPANY = this.txtguest_company.Text.Trim();
                S_model.TYPE_ID = Convert.ToInt32(this.txttypeid.Text.Trim());
                S_model.USER_NAME = this.txtuser_name.Text.Trim();
                int i = B_S.B_Supdate(S_model);
                if (i > 0)
                {
                    Response.Write("<script>alert('更新成功！'):window.location.href='server.aspx'</script>");
                }
                else
                {
                    Response.Write("<script>alert('更新失败！')</script>");
                }
            }
           else
            {
                Response.Write("没有找到相关内容！");
            
            }        }