C# 父子页面传值

业务需求是：父页面点击“选择任务”按钮进入任务列表页。（项目进度周报）

　　父页面如下：

任务列表页：

　　

选择某一个任务，点击“确定”后返回父页面所需数据。

父页面“选择任务” 按钮触发事件。

        /// <summary>
        /// 选择任务按钮
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void btnSelectTask_Click(object sender, EventArgs e)
        {
            string GantId = Request.QueryString["gantid"];
            string gantTaskIds = Request.QueryString["gantTaskIds"];
            string urlParams = string.Format("?GantId={0}&gantTaskIds={1}", GantId, gantTaskIds);
            string openUrl = "SelectTask.aspx" + urlParams;
            //打开选择任务页面
            PageContext.RegisterStartupScript(Window1.GetSaveStateReference(hfNewTaskID.ClientID, hfNewTaskUID.ClientID,lblTaskName.ClientID, 
                                                  lblPlanInfo.ClientID, lblProgressNow.ClientID, hfProgressNow.ClientID) 
                                              + Window1.GetShowReference(openUrl));
        }

任务列表页面，确定按钮事件：

//确定按钮
        protected void btnConfirm_Click(object sender, EventArgs e)
        {
            var firstRowDataKeys = GridUtil.GetFirstSelected(Grid1, 6);
            if (firstRowDataKeys == null)
            {
                Alert.Show("请选择一项！", MessageBoxIcon.Warning);
            }
            else
            {
                //Id,UID,ProjectId,Name,days
                string id = firstRowDataKeys[0];
                string uid = firstRowDataKeys[1];
                string name= firstRowDataKeys[3];
                string days = firstRowDataKeys[4];
                string planInfo= firstRowDataKeys[5];
                //选定以后查询本任务对应的最新进度
                string gantId = Request.QueryString["gantid"];
                if (!string.IsNullOrWhiteSpace(id)&& !string.IsNullOrWhiteSpace(uid) && !string.IsNullOrWhiteSpace(gantId))
                {
                    string progressNow = pwtBll.GetTaskProgressNow(gantId, uid, id);
                    PageContext.RegisterStartupScript(ActiveWindow.GetWriteBackValueReference(id, uid, name, planInfo, progressNow, progressNow) + ActiveWindow.GetHideReference());
                    
                }
            }
        }