msdn官方示例：http://msdn.microsoft.com/zh-cn/library/bb398934%28v=VS.90%29.aspx
总的来说，
1，注册ScriptManager的AsyncPostBackError事件，并在服务器实现它，并抛出被处理过的异常（根据是否为null,可能需要抛出e.Exception或e.Exception.innerException）
2，客户端用JS来响应，Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);添加处理程序
3，实现EndRequestHandler，错误信息基本在第二个参数"args“里面，
4，此时已经完成，由于网上没搜到现成文档（有的话请留言），这个args里面到底有什么经过我的枚举，暂列如下
内容比较多，我还是先把枚举的方法写出来吧：
注：下面内容是临时写的，并没有用到递归，也就是说，可能结果还不是完整的，有兴趣的可以自己拿去改造
但我们一般用到的，基本上都在了
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);
function EndRequestHandler(sender, args) {
//if (args.get_error() != undefined) {alert(args.get_error().message.replace(/.*Exception:/,'')); args.set_errorHandled(true); }
if (args.get_error() != undefined) {
var members = 'The \'args\' members are:\n\n';
for (var i in args) {
members += '\t' + i;
var ai = eval("args." + i);
if (typeof ai == "function") {
try {
members += "()";
ai = eval("args." + i+"()");
} catch (err) {
members += " not implement \n";
continue;
}
}
members += '\n';
if (typeof ai == "string") continue;
for (var t in ai) {
members += '\t\t' + t;
if (typeof ai == "function")
var ait = eval("args." + i + "()." + t);
else
var ait = eval("args." + i + "." + t);
if (typeof ait == "function") {
try {
members += "()";
ait = eval("args." + i + "." + t + "()");
} catch (err) {
members += " not implement \n";
continue;
}
}
members += "\n";
if (typeof ait == "string") continue;
for (var m in ait) {
members += '\t\t\t' + m + '\n';
}
}
}
document.write("<textarea style='1000px; height:600px;'>"+members+"</textarea>");//members如果显示请自行处理
args.set_errorHandled(true);
}
}结果：
The 'args' members are: _errorHandled _error message name httpStatusCode format localeFormat _toFormattedString stack fileName lineNumber format localeFormat _toFormattedString popStackFrame() _dataItems _response _webRequest _url _headers _body _userContext _httpVerb _executor _invokeCalled _timeout _events add_completed remove_completed completed _get_eventHandlerList get_url set_url get_headers get_httpVerb set_httpVerb get_body set_body get_userContext set_userContext get_executor set_executor get_timeout set_timeout getResolvedUrl invoke constructor _resultObject _xmlHttpRequest dispatchEvent removeEventListener onreadystatechange open readyState setRequestHeader send status responseText channel responseXML statusText abort getAllResponseHeaders getResponseHeader sendAsBinary overrideMimeType multipart mozBackgroundRequest withCredentials upload onuploadprogress onabort onerror onload onloadstart onprogress getInterface _responseAvailable _timedOut _timer _aborted _started _onReadyStateChange() _clearTimer() _onTimeout() get_timedOut() get_started() get_responseAvailable() get_aborted() executeRequest() not implement getResponseHeader() not implement getAllResponseHeaders() not implement get_responseData() not implement get_statusCode() not implement get_statusText() not implement get_xml() not implement abort() constructor() get_webRequest() _set_webRequest() get_object() not implement get_dataItems() get_error() message name httpStatusCode stack fileName lineNumber popStackFrame get_errorHandled() set_errorHandled() not implement get_response() _webRequest _resultObject _xmlHttpRequest _responseAvailable _timedOut _timer _aborted _started _onReadyStateChange _clearTimer _onTimeout get_timedOut get_started get_responseAvailable get_aborted executeRequest getResponseHeader getAllResponseHeaders get_responseData get_statusCode get_statusText get_xml abort constructor() callBaseMethod getBaseMethod getBaseType getInterfaces getName implementsInterface inheritsFrom initializeBase isImplementedBy isInstanceOfType registerClass registerInterface resolveInheritance registerEnum get_webRequest _set_webRequest get_object constructor() not implement