首先看下面的代码片段，我们希望用户在点击页面上的Button时首先将数据提交到指定的第三方页面，然后再执行后台的Page_Load事件。
<body>
<iframe id="WebGatewaySubmissionProcessor_IFrame" name="WebGatewaySubmissionProcessor_IFrame" style="display: none;"></iframe>
<form onsubmit="javascript:if (typeof WebGatewayDoubleSubmission != 'undefined') {WebGatewayDoubleSubmission(this);}" id="Form1" runat="server">
<div id="page">
<asp:Button ID="BtnClientSend" runat="server" />
</div>
<script type="text/javascript" id="WebGatewayScript">
WebGatewayDoubleSubmission = function(o) {
var oldAction = o.action;
var oldOnSubmit = o.onsubmit;
var oldTarget = o.target;
var oldMethod = o.method;
var iframeSubmisionTarget = document.getElementById("WebGatewaySubmissionProcessor_IFrame");
var submitPostIframeSubmission = function() {
o.action = oldAction;
o.target = oldTarget;
o.method = oldMethod;
o.onsubmit = oldOnSubmit;
o.submit();
};
/*iframeSubmisionTarget.onload = submitPostIframeSubmission;*/
eventPush(iframeSubmisionTarget, 'load', submitPostIframeSubmission);
o.action = "http://webgateway.hostedmscrm.com/V2/formprocessor.aspx";
o.target = "WebGatewaySubmissionProcessor_IFrame";
o.onsubmit = null;
o.method = "POST";
o.submit();
};
WebGatewaySubmission = function(o) {
o.action = "http://webgateway.hostedmscrm.com/V2/formprocessor.aspx";
o.method = "POST";
};
function eventPush(obj, event, handler) {
if (obj.addEventListener) {
obj.addEventListener(event, handler, false);
} else if (obj.attachEvent) {
obj.attachEvent('on' + event, handler);
}
}
</script>
</form>
</body>
Form中的onsubmit事件在页面被提交时触发，此时首先执行WebGatewayDoubleSubmission脚本方法，在该方法中，将当前Form的action，onsubmit，target，method缓存到指定的变量中，然后将Form的action和target指向另一个页面进行提交，此时页面上的数据被Post到第三方页面。然后再使用页面上隐藏的IFrame来调用submitPostIframeSubmission方法，并将原先的Form进行提交。这里有一个问题，在上面的代码中有一行被注释掉了，原因就是直接使用IFrame的onload方法并不能触发该事件，从而导致submitPostIframeSubmission方法不能执行，页面的第二次提交不成功！使用eventPush方法可以有效地解决该问题。
