下拉OnSelectedIndexChanged没有开火

Question

下拉OnSelectedIndexChanged没有开火

Jim*_*Jim 3 c# asp.net autopostback selectedindexchanged drop-down-menu

OnSelectedIndexChanged我的下拉框没有触发该事件.我看过的所有论坛都告诉我添加AutoPostBack="true",但这并没有改变结果.

HTML:

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
      <asp:Label ID="Label1" runat="server" Text="Current Time:  " /><br />
      <asp:Label ID="lblCurrent" runat="server" Text="Label" /><br /><br />
      <asp:DropDownList ID="cboSelectedLocation" runat="server" AutoPostBack="true" OnSelectedIndexChanged="cboSelectedLocation_SelectedIndexChanged"  /><br /><br />
      <asp:Label ID="lblSelectedTime" runat="server" Text="Label" />
    </div>
    </form>
</body>
</html>

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代码背后:

public partial class _Default : Page 
{
    string _sLocation = string.Empty;
    string _sCurrentLoc = string.Empty;
    TimeSpan _tsSelectedTime;

    protected void Page_Load(object sender, EventArgs e)
    {
      AddTimeZones();
      cboSelectedLocation.Focus();
      lblCurrent.Text = "Currently in " + _sCurrentLoc + Environment.NewLine + DateTime.Now;
      lblSelectedTime.Text = _sLocation + ":" + Environment.NewLine + DateTime.UtcNow.Add(_tsSelectedTime);
    }

    //adds all timezone displaynames to combobox
    //defaults combo location to seoul, South Korea
    //defaults current location to current location
    private void AddTimeZones()
    {
      foreach(TimeZoneInfo tz in System.TimeZoneInfo.GetSystemTimeZones())
      {
        string s = tz.DisplayName;
        cboSelectedLocation.Items.Add(s);
        if (tz.StandardName  == "Korea Standard Time") cboSelectedLocation.Text = s;
        if (tz.StandardName == System.TimeZone.CurrentTimeZone.StandardName) _sCurrentLoc = tz.StandardName;
      }
    }

    //changes timezone name and time depending on what is selected in the cbobox.
    protected void cboSelectedLocation_SelectedIndexChanged(object sender, EventArgs e)
    {
      foreach (TimeZoneInfo tz in System.TimeZoneInfo.GetSystemTimeZones())
      {
        if (cboSelectedLocation.Text == tz.DisplayName)
        {
          _sLocation = tz.StandardName;
          _tsSelectedTime = tz.GetUtcOffset(DateTime.UtcNow);
        }
      }
    }
}

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关于新手asp编程器应该注意什么的建议？

编辑:添加更多代码

Graham Clark在需要时是正确的!Page.IsPostBack,但它现在是我设置的全局变量的东西.这段代码是从ac#项目中拖放的,所以我假设全局变量和asp.net存在一些问题.我有时间对此进行更多研究,以了解全局变量如何在独立而不是Web程序中有所不同.

Answer 1

Gra*_*ark 9

您是将每次旅行的下拉列表数据绑定回服务器,还是只回发？如果你每次都这样做,可能是服务器认为没有选择任何东西,因此事件不会触发.

假设您正在对Page_Load事件中的下拉列表进行数据绑定.你想这样做:

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        // bind drop-down list here
    }
}

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