如何判断ASP中的页面卸载是否为回发 [英] How to tell if a page unload in ASP is a PostBack

问题描述

这似乎是一个常见问题，但搜索未返回任何内容.

This seems like a common question but search is not returning anything.

我有以下代码在页面卸载之前执行.问题是如果卸载是回发，我不想向用户发出警告，但我不知道如何区分回发和例如，用户导航到另一个页面.

I have the following code that executes before the page unloads.The problem is if the unload is a postback i do not want to fire my warning to the user but i can't figure out how to differentiate between a postback and a user navigating to another page for example.

// This is executed before the page actually unloads
        $(window).bind("beforeunload", function () {

            if (prompt) {

                //prompt
                return true;
            }
            else {

                //reset our prompt variable
                prompt = true;
            }
        })

在代码背后运行脚本，即如果Page.IsPostBack然后设置提示不是选项.

Running script in the code behind i.e. if Page.IsPostBack then set prompt is not an option.

有什么想法吗?

这是我最终得到的解决方案:

Here is the solution I ended up with:

 function DoNotPrompt() {
              prompt = false;
        }

然后我将其添加到所有控件中，用户可以在这些控件中做一些会导致回发的操作.

I then added this to all the controls where the user could do something that result in a post back.

OnClientClick="DoNotPrompt()

然后检查此标志，如果用户确实离开页面即不回发，则仅在"beforeunload"中返回字符串.

Then checked this flag and only returned a string in "beforeunload" if the user was really moving away from the page i.e. not a postback.

我还必须使用以下代码: var magicInput = document.getElementById('__ EVENTTARGET');

I also had to use this code: var magicInput = document.getElementById('__EVENTTARGET');

    if (magicInput && magicInput.value) {
        // the page is being posted back by an ASP control 
        prompt = false;
    }

原因是我有一个自定义用户控件，该控件是一个列表框，因此我无法添加上述方法.因此，用它来捕获该事件并将标志设置为false.

The reason being i had a custom user control that was a list box and I could not add the above method. So used this to catch that event and set the flag to false.

不是最精致的解决方案.

Not the most elegent solution.

谢谢， 迈克尔

推荐答案

这可能无法涵盖所有​​回发情况，但是您可以通过查询__EVENTTARGET隐藏输入来判断页面是否由ASP控件回发了.

This may not cover all of the postback situations, but you can tell if the page was posted back by an ASP control by interrogating the __EVENTTARGET hidden input.

当ASP控件将页面发回时，此输入由ASP设置.

This input is set by ASP when the page is posted back by an ASP control.

var magicInput = document.getElementById('__EVENTTARGET');

if (magicInput && magicInput.value) {
   // the page is being posted back by an ASP control
}

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