C# 单击表格单元格时，动态创建的Asp表格将不可见

我正在处理一个项目，因为我有一个用于选择类的下拉列表。然后，对于所选类，将显示其时间表。我使用asp表格动态创建了此时间表，并在表格单元格上添加了单击事件。但是，当我单击表格单元格时，整个表格将不可见。我以前使用asp表格执行相同类型的操作东西，当时我也遇到了同样的错误，但当我在页面加载事件中将create table方法放在post back方法之外时，它得到了解决。但在这里，我在下拉选择的索引更改时调用了create time table方法。我尝试将asp表放在更新面板中，但这也没有解决我的问题

下面是我的aspx代码

<asp:Panel ID="pnltimetable" runat="server" Visible="false">
       <asp:Table ID="tbltimetable" CssClass="timetable" runat="server"  CellSpacing="25" GridLines="Both"></asp:Table>
    </asp:Panel>

下面是我的cs代码

protected void Page_Load(object sender, EventArgs e)
{
    if (Session["UserType"] == null)
    {
        Response.Redirect("Login.aspx");
    }
    if (!IsPostBack)
    {
        filldrpclass();
    }
}
//method for making timetable
protected void makeTimetable()
{
    string periodno = "";
    //getting all periods
    sql = "SELECT * FROM tblperiodtime order by periodnumber";
    ds = obj.openDataset(sql, Session["schoolcode"].ToString());
    //getting timetable of the selected class
    sql = "SELECT t.*,s.subjectname,tc.teachername FROM tbltimetable t join tblsubject s on s.sshortname=t.subject join tblteacher tc on tc.tshortname=t.tchrshortnm where t.classcode='" + drpclass.SelectedItem.Value + "' order by t.period";
    DataSet dsTimetbl = new DataSet();
    dsTimetbl = obj.openDataset(sql, Session["schoolcode"].ToString());
    DataRow[] drtimetbl;        
    //To clear previously added rows
    tbltimetable.Rows.Clear();        
    //some entries exists for periods
    if (ds.Tables[0].Rows.Count != 0)
    {
        for (int i = 0; i < ds.Tables[0].Rows.Count + 1; i++)
        {
            TableRow tr = new TableRow();
            for (int j = 0; j < 7; j++)
            {
                TableCell tc = new TableCell();
                if (i == 0)
                {
                    tc.CssClass = "periodTableCelldays";
                    tc.HorizontalAlign = HorizontalAlign.Center;
                    if (j == 0)
                        tc.Text = "Periods";
                    else
                    {
                        //get week day name from integer value
                        string weekday = System.Globalization.CultureInfo.CurrentCulture.DateTimeFormat.DayNames[j];
                        //for displaying text in the form of Weekday eg MON
                        tc.Text = (weekday.Substring(0, 3)).ToUpper();
                    }
                    tr.Cells.Add(tc);
                    tbltimetable.Rows.Add(tr);
                }
                else
                {
                    tc.HorizontalAlign = HorizontalAlign.Center;
                    if (j == 0)
                    {
                        //showing period number and timing
                        tc.CssClass = "periodtime";
                        tc.Text = "0" + ds.Tables[0].Rows[i - 1]["periodnumber"].ToString() + "<br/>" + ds.Tables[0].Rows[i - 1]["starttime"].ToString() + "-" + ds.Tables[0].Rows[i - 1]["stoptime"].ToString();
                        periodno = "0" + ds.Tables[0].Rows[i - 1]["periodnumber"].ToString();
                        tr.Cells.Add(tc);
                    }
                    else
                    {                           
                        //selecting particular period
                        drtimetbl = dsTimetbl.Tables[0].Select("period='" + periodno + "' and weekday='" + j + "'");
                        clickablecell ctCell = new clickablecell();
                        ctCell.HorizontalAlign = HorizontalAlign.Center;
                        if (drtimetbl.Length != 0)
                        {
                            ctCell.CssClass = "viewlessonplan";
                            Random rnd = new Random();
                            ctCell.ID = j + "-" + periodno + "-" + ds.Tables[0].Rows[i - 1]["starttime"].ToString() + "-" + ds.Tables[0].Rows[i - 1]["stoptime"].ToString() + "-" + "Edit-" + drtimetbl[0]["id"].ToString() + "-" + "Subject-" + drtimetbl[0]["subjectname"].ToString() + "-" + "Teacher-" + drtimetbl[0]["teachername"].ToString();
                            //ctCell.ID = drtimetbl[0]["id"].ToString() + "-" + (i * j + i + j).ToString();
                            ctCell.Text = drtimetbl[0]["subjectname"].ToString() + "<br/> by<br/>" + drtimetbl[0]["teachername"].ToString() + "<br/>Edit Period";
                            ctCell.Attributes.Add("onmouseover", "defColor=this.style.backgroundColor;  this.style.backgroundColor='LightGray';");
                            ctCell.Attributes.Add("onmouseout", "this.style.backgroundColor=defColor;");
                            ctCell.Click += new clickablecell.ClickEventHandler(textcell_Click);
                        }
                        else
                        {                               
                            ctCell.Text = "Create Period";
                            //weekday-period-starttime-stoptime
                            ctCell.ID = j + "-" + periodno + "-" + ds.Tables[0].Rows[i - 1]["starttime"].ToString() + "-" + ds.Tables[0].Rows[i - 1]["stoptime"].ToString()+"-Create-0-Subject-null-Teacher-null";
                            ctCell.CssClass = "noperiod";
                        }
                        tr.Cells.Add(ctCell);
                    }
                    tbltimetable.Rows.Add(tr);
                }
            }
        }
        tbltimetable.Visible = true;
        pnltimetable.Visible = true;
    }
    //if no entries exists for periods
    else
    {
        tbltimetable.Visible = false;
        pnltimetable.Visible = false;
        lblalerts.Text = "Time Table/Lesson Plan not created yet";
        lblalerts.Visible = true;
        divalerts.Visible = true;
    }
}
//table cell's click event
void textcell_Click(object sender, EventArgs e)
{
    makeTimetable();
    clickablecell _ctcell = (clickablecell)sender;
    string weekday = (_ctcell.ID.Split('-')[0]).ToString();
    string period = (_ctcell.ID.Split('-')[1]).ToString();
    string starttime = (_ctcell.ID.Split('-')[2]).ToString();
    string stoptime = (_ctcell.ID.Split('-')[3]).ToString();
    string operationtype = (_ctcell.ID.Split('-')[4]).ToString();
    string timetableid = (_ctcell.ID.Split('-')[5]).ToString();
    string subjectname = (_ctcell.ID.Split('-')[7]).ToString();
    string teachername = (_ctcell.ID.Split('-')[9]).ToString();
    if (operationtype == "Edit")
    {
        lbledit_heading.Text = "Edit Period";
        //for preselecting subjects when edit period is selected
        foreach (ListItem li in drpSubjects.Items)
        {
            if (li.Text == subjectname)
                li.Selected = true;
        }
        //for preselecting days
        foreach (ListItem li in drpDays.Items)
        {
            if (li.Value == weekday)
                li.Selected = true;
        }
        //for preselecting teachers
        foreach (ListItem li in drpteachers.Items)
        {
            if (li.Text == teachername)
                li.Selected = true;
        }
    }
    else
        lbledit_heading.Text = "Create Period";
    //filling controls in popup
    filldrpsubjects();
    filldrpteachers();
    lnkHidden_ModalPopupExtender.Show();
}

受保护的无效页面加载（对象发送方，事件参数e）
{
if（会话[“用户类型”]==null）
{
重定向（“Login.aspx”）；
}
如果（！IsPostBack）
{
filldrpclass（）；
}
}
//制定时间表的方法
受保护的无效时间表（）
{
字符串周期号=”；
//获取所有周期
sql=“按时段编号从tblperiodtime顺序中选择*”；
ds=obj.openDataset（sql，会话[“学校代码”].ToString（））；
//获取所选课程的时间表
sql=“从tbltimetable中选择t.*，s.subjectname，tc.teachername在s.sshortname=t上加入tblsubject，在tc.tshortname=t.tchrshortnm上加入TBLTacher tc，其中t.classcode=”“+drpclass.SelectedItem.Value+“'order by t.period”；
数据集DSTIMEBL=新数据集（）；
dsTimetbl=obj.openDataset（sql，会话[“学校代码”].ToString（））；
DataRow[]drtimetbl；
//清除以前添加的行的步骤
tbltimetable.Rows.Clear（）；
//某些条目存在于期间
if（ds.Tables[0].Rows.Count！=0）
{
对于（int i=0；i”+drtimetbl[0][“teachername”]。ToString（）+“
编辑期间”；
添加（“onmouseover”，“defColor=this.style.backgroundColor；this.style.backgroundColor='LightGray'；”；
ctCell.Attributes.Add（“onmouseout”，“this.style.backgroundColor=defColor；”）；
ctCell.Click+=新建clickablecell.ClickEventHandler（textcell\u Click）；
}
其他的
{                               
ctCell.Text=“创建期间”；
//工作日期间开始时间停止时间
ctCell.ID=j+“-”+periodno+“-”+ds.Tables[0]。行[i-1][“starttime”]。ToString（）+“-”+ds.Tables[0]。行[i-1][“stoptime”]。ToString（）+“-创建-0-Subject-null-Teacher-null”；
ctCell.CssClass=“noperiod”；
}
tr.Cells.Add（ctCell）；
}
tbltimetable.Rows.Add（tr）；
}
}
}
tbltimetable.Visible=true；
pnltimetable.Visible=true；
}
//如果期间不存在任何条目
其他的
{
tbltimetable.Visible=false；
pnltimetable.Visible=false；
lblalerts.Text=“未创建时间表/课程计划
Visible="false"

protected void Page_Load(object sender, EventArgs e)
{
    if (Session["UserType"] == null)
    {
        Response.Redirect("Login.aspx");
    }
    if (!IsPostBack)
    {
        filldrpclass();
        pnltimetable.Visible = false; //initially hidden
    }
}