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    <p>I finally got around to stepping through MicrosoftAjaxWebForms.debug.js and verified that the PageRequestManager does indeed generate the post collection prior to raising the beginRequest event. Worse, the collection is stored in a StringBuilder in a local variable, so I couldn't manipulate it, even if I was willing to access private members.</p> <p>The solution I found was to call ScriptManager.RegisterOnSubmitStatement from Page_Load in code behind, to setup a JavaScript beforePostback() function. I verified that this function does indeed get called before the PageRequestManager begins its dirty work, so I was able to put my calls to removeNonEssentialPostBackValues() in there.</p> <pre><code> If Not ScriptManager.GetCurrent(Me).IsInAsyncPostBack Then ScriptManager.RegisterOnSubmitStatement(Me, Me.GetType(), "beforePostback", "beforePostback()") End If </code></pre> <p>And the JavaScript:</p> <pre><code>function beforePostback() { var nlTriggers = document.getElementsByName(document.aspnetForm.__EVENTTARGET.value); if (nlTriggers &amp;&amp; nlTriggers.length &gt; 0) { var elPostBackTrigger = nlTriggers[0]; } // skip the first input element, which is expected to be the ScriptManager's hidden field removeNonEssentialPostBackValues(document.aspnetForm.getElementsByTagName("input"), elPostBackTrigger, 1); removeNonEssentialPostBackValues(document.aspnetForm.getElementsByTagName("select"), elPostBackTrigger); removeNonEssentialPostBackValues(document.aspnetForm.getElementsByTagName("textarea"), elPostBackTrigger); } </code></pre> <p>With this code, I found that I could reduce the size of the postback request in my hand-crafted nightmare scenario from about 34K down to about 15K. I also verified that the important form values were still getting passed through to the page, and that the code-behind could still discern which element triggered the postback.</p> <p>Obviously, this technique is quite heavy-handed, and would not fit many scenarios. For example, in a typical web form scenario where the user must edit multiple fields and pass validation, you wouldn't want to do this, because you would <em>need</em> all the form values to be posted. Really, this technique is a simple way of getting closer to a client-side interface where the JavaScript makes only the minimum server calls necessary to carry out its commands. I've built such applications before and while their performance is very good, they are tedious to develop and maintain. For this project I wanted to leverage ASP.NET as much as possible while maintaining high performance.</p> <p><strong>UPDATE:</strong> I just tested this in IE 8 (I had been using Firefox 3.6) and it is a very slow process to disable the hundreds/thousands of form elements. It takes 1 or 2 seconds, unlike Firefox 3.6, which doesn't even blink. I shudder to think how slow IE 7 might be. I guess I will have to abandon this technique for now, since the delay introduced for the large amount of IE users would be much greater than the delay caused by the extra 20K of postback data for the unnecessary form elements.</p>
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    1. POHow do I disable or remove unnecessary form elements before an ASP.NET asynchronous postback?
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    1. POHow do I disable or remove unnecessary form elements before an ASP.NET asynchronous postback?
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