ASP.Net 1.x的client side postback script是这样的：
<!--
function __doPostBack(eventTarget, eventArgument) {
var theform;
if (window.navigator.appName.toLowerCase().indexOf("netscape") > -1) {
theform = document.forms["Form1"];
}
else {
theform = document.Form1;
}
theform.__EVENTTARGET.value = eventTarget.split("$").join(":");
theform.__EVENTARGUMENT.value = eventArgument;
theform.submit();
}
// -->

它是通过form.submit()去submit的。这样就有一个问题，form.onsubmit事件不会被触发，这么一来可能有些client side validation script就被绕过了。在ASP.Net 2.0里，这个问题被fix了。对于ASP.Net 1.x，据我所知，SP1也没有解决这个问题。我们可以使用下面的代码解决这个问题：

string myDoPostBack = @"
<script language=""javascript"">
<!--
function __myDoPostBack(eventTarget, eventArgument) {
var theform;
if (window.navigator.appName.toLowerCase().indexOf(""netscape"") > -1) {
theform = document.forms[""Form1""];
}
else {
theform = document.Form1;
}
theform.__EVENTTARGET.value = eventTarget.split(""$"").join("":"");
theform.__EVENTARGUMENT.value = eventArgument;
if ((typeof(theform.onsubmit) == ""function"") && theform.onsubmit()!=false) {
theform.submit();
}

}
__doPostBack = __myDoPostBack
// -->
</script>";
RegisterStartupScript("myDoPostBack", myDoPostBack);