VS 2008
本文介绍在异步提交过程中发挥着重大作用的客户端 PageRequestManager对象。
1. PageRequestManager 客户端事件模型
PageRequestManager是一个客户端的javascript对象，当发生异步postback请求时，伴随之一系列的事件发生
有了这个事件模型，在客户端，我们便可以跟踪异步postback过程，可以做一些特别的处理等。
2. 跟踪异步处理过程
页面中放置了ScriptManager控件，和一个UpdatePanel控件，然后放了一个divProgress，用于显示一些提示信息
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<div>
<asp:UpdatePanel ID="uPanel1" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<asp:TextBox ID="txtUserName" runat="server" />
<asp:Button ID="btnShowName" runat="server" Text="show name"
onclick="btnShowName_Click" />
</ContentTemplate>
</asp:UpdatePanel>
<div id="divProgress"></div>
</div>
btnShowName的Click处理方法，用Thread.Sleep模拟提交结果返回的延时
protected void btnShowName_Click(object sender, EventArgs e) 
{
System.Threading.Thread.Sleep(2000);
txtUserName.Text = "guozhijian";
}
现在看javascript：
<script type="text/javascript">
function pageLoad() {
var req = Sys.WebForms.PageRequestManager.getInstance();
req.add_beginRequest(function(sender, eventArgs) {
$get('divProgress').innerHTML = "loading";
});
req.add_endRequest(function(sender, eventArgs) {
$get('divProgress').innerHTML = "";
});
}
</script>
当点击btnShowName开始异步请求时，beginRequest事件发生，divProgress显示："loading..."。
然后endRequest事件发生，divProgress显示信息被clear了，文本框显示"guozhijian"。
3. 中断异步回刷请求
在UpdatePanel中添加一个btnCancel控件：
<div>
<asp:UpdatePanel ID="uPanel1" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<asp:TextBox ID="txtUserName" runat="server" />
<asp:Button ID="btnShowName" runat="server" Text="show name"
onclick="btnShowName_Click" />
<asp:Button ID="btnCancel" runat="server" Text="cancel" />
</ContentTemplate>
</asp:UpdatePanel>
<div id="divProgress"></div>
</div>
(suddenly I can't input chinese -.-! so i have no choice but use english in substitution for chinese)
then, i am going to modify the javascript, I call the argument's get_postBackElement() function and get the id property's value, if the value equals 'btnCancel', then I know that the btnCancel button was just clicked, so I call the req's abortPostBack() function.
note that although the partial page rendering request has been aborted, the endRequest event still gonna happen!
<script type="text/javascript">
function pageLoad() {
var req = Sys.WebForms.PageRequestManager.getInstance();
req.add_beginRequest(function(sender, args) {
$get('divProgress').innerHTML = "loading";
if(args.get_postBackElement().id == 'btnCancel') {
req.abortPostBack();
}
});
req.add_endRequest(function(sender, args) {
$get('divProgress').innerHTML = "";
});
}
</script>
4. 异常处理
Also, we can use PageRequestManager for handling exception.
Let the btnShowName_Click method throw an exception:
protected void btnShowName_Click(object sender, EventArgs e) {
throw new Exception("an error occured");
txtUserName.Text = "guozhijian";
}
Regardless of whether an error occurs during an asynchronous postback, the PageRequestManager raises the endRequest event, so we write error handling code like this:
req.add_endRequest(function(sender, args) {
$get('divProgress').innerHTML = args.get_error().message;
args.set_errorHandled(true);
});
don't forget to write the line : args.set_errorHandled(true), or an window alert box will show unexpectedly.
posted on 2008-02-20 21:21
Tristan(GuoZhijian) 阅读(325)
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Asp.Net Ajax