下拉 OnSelectedIndexChanged 未触发
我的下拉框没有触发 OnSelectedIndexChanged 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>
代码隐藏：
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);
}
}
}
}
对于新手 asp 编码员应该注意什么有什么建议吗？
编辑：在
Graham Clark 后面添加更多代码是正确的，需要 !Page.IsPostBack，但现在它是我设置的全局变量的东西。该代码是从 ac# 项目中拖放的，因此我认为全局变量和 asp.net 存在一些问题。我是时候对此进行更多研究，以了解全局变量在独立程序与 Web 程序中有何不同。
The OnSelectedIndexChanged event is not firing for my dropdown box. All forums I have looked at told me to add the AutoPostBack="true", but that didn't change the results.
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>
Code behind:
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);
}
}
}
}
Any advice into what to look at for a rookie asp coder?
EDIT: added more code behind
Graham Clark was correct in needing the !Page.IsPostBack, but it is now something with the global variables that I set. This code was dragged and dropped from a c# project, so I assume there is some issues with global variables and asp.net. Time for me to do more research on this to understand how global variables differ in a standalone as opposed to a web program.
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您是否在每次返回服务器时都对下拉列表进行数据绑定，或者只是在回发时进行数据绑定？如果您每次都这样做，则可能是服务器认为没有选择任何内容，因此事件不会触发。
假设您正在 Page_Load 事件中的下拉列表中进行数据绑定。你想这样做：
Are you databinding your drop-down list every trip back to the server, or just on a postback? If you're doing it every time, it could be that the server doesn't think anything has been selected, therefore the event won't fire.
Say you're databinding the drop-down in the Page_Load event. You want to do it like this: