Why this button doesn't cause triple postback?

We have developed a page with a asp.net and debugging it accidentally we have discovered on our page button with the next code on onclik attribute

onclick="__doPostBack('ctl00$FormPlace$m_userTaskMarkAsUnreadButton',''); __doPostBack('ctl00$FormPlace$m_userTaskMarkAsUnreadButton','');WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions("ctl00$FormPlace$m_userTaskMarkAsUnreadButton", "", true, "", "", false, false))"

It seems that the button do three postbacks but when we click it only cause on postback. With this code seems that de button will cause three postbac开发者_开发问答ks!!

We have try it with Internet Explorer and Firefox and the button only cause on postback always. Are browsers who avoid that the button do three postback ? Or Is Asp.net server who avoid the three postback? We don't understand why the button behaves correctly if onclick attribute has three call to do Postbacks.

Thanks

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If the first JavaScript function called causes the page to POST your data (not using an XMLHttpRequest), a new page is loaded and the execution of your JavaScript stops.

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The first __doPostback will post the page immediately. The remaining two statements will never be executed.

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__doPostBack fills two hiddenfields with the given parameters and then does a submit to the server. Everything what comes later in the javascript is irrelevant because the page will be destroyed and rebuilded.

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I know I’m reinventing the wheel here... but __doPostBack actually.. does postback so when first __doPostBack is executed the page you’re on is already gone.

And btw, doing it that way sounds very dodgy.. why not call one method and do it 3 times in the back-end?

Also.. it depends whether or not you are using UpdatePanels..