blocks|key|361841|text|TempData使用了Session对象AFAIK，它不会遇到这个问题。你在这方面遇到过什么特殊的问题吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|361842|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

TempData makes use of the Session object, which does not suffer this problem, AFAIK. Have you run into a specific problem with this?

blocks|key|358528|text|好的，浏览ASP.NET+MVC代码可以看到，虽然TempData存储在会话中，但在加载时，它会从会话中删除。并将其加载到控制器的ExecuteCore()方法中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|358529|因此，我认为这将意味着是的，您完全可以遇到来自不同浏览器选项卡的请求可能导致此问题的竞争条件(您有一个非常好的示例)。但这将取决于每个浏览器处理请求的模型。浏览器可能会将所有请求序列化到同一服务器，以便一次只执行一个请求。但实际上，他们不会这么做，他们会将其限制在最大值，即(我认为)对同一服务器的5个并发请求。|358530|鉴于ASP.NET+MVC站点可以是对任何浏览器(毕竟是web+:)的服务请求，这是一个真实的场景，尽管如您所说，这可能是一个罕见的场景。|358531|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

Well, browsing the ASP.NET MVC code shows that the while TempData is stored in the session, it is removed from the session when it is loaded. And it gets loaded in the Controller's ExecuteCore() method.

So I think that would mean that yes, you entirely could run into a race condition where a request from a different browser tab (you had a pretty good example) could cause this problem. But that would depend on each browser's model for handling requests. A browser might serialize all requests to the same server so that only one executes at a time. In reality, they won't do that, though, they'll cap it at the max which is (I think) 5 concurrent requests to the same server.

Given that an ASP.NET MVC site could be services requests to any browser (it's the web, afterall :) ) it is a real scenario, albeit probably a rare one, as you said.

blocks|key|357190|text|在使用TempData时，完全有可能出现竞争条件。然而，在正常使用的情况下，你当然必须“倒霉”。为了遇到竞争条件，必须满足以下所有条件：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|357191|357192|您必须首先使用TempData。|ordered-list-item|357193|您必须打开多个浏览器窗口/选项卡/任何内容，并共享同一浏览器会话。|357194|来自第二个浏览器选项卡的请求必须在第一个浏览器选项卡的请求和响应之间“潜入”。|357195|357196|请注意，第2项在很大程度上取决于您使用的浏览器。根据IE的设置，打开多个窗口并不意味着它们共享浏览器cookies，因此它们不一定共享会话(基于cookies)。|357197|但是，如果遇到某个东西就会爆炸，这就不存在竞争条件了。这可能就是Haacked所指的。但是，您可以在某种意义上达到竞争条件，即您在一个请求中设置了一些TempData，然后在您认为将获得它的下一个请求中没有得到它。它只会是空的。|357198|谢谢，Eilon|357199|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|T|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|U|8|@]|9|@]|A|$]]|$1|F|3|G|5|E|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|E|7|W|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|R|$]]

It is entirely possible to have a race condition when using TempData. However, you'd have to of course be "unlucky" to experience it under normal usage. In order to run into the race condition the following must all be true:

<ol>
<li>You have to be using TempData to begin with.</li>
<li>You have to have multiple browser windows/tabs/whatevers open and sharing the same browser session.</li>
<li>A request from the second browser tab has to "sneak in" between the request and response of the first browser tab.</li>
</ol>

Note that item #2 depends a lot on which browser you're using. Depending on how you have IE set up, just because you have multiple windows opened does not mean that they share browser cookies, and thus they do not necessarily share sessions (which are based on cookies).

However, there is no race condition in the sense that something explodes if you run into it. That might be what Haacked is refering to. But you can hit a race condition in the sense that you set some TempData in one request and then didn't get it back in the next request where you thought you were going to get it. It'll just be empty.

Thanks,
Eilon

blocks|key|361945|text|我认为这永远不会发生，尽管在一开始我有相同的confusion.Think，如果你在调试模式下运行你的mvc应用程序，然后你在重定向操作.And中设置一个断点，然后你给tempdata一个值，然后你会在重定向viewResult和其他视图中得到tempdate，你会发现其他请求永远不会响应，直到重定向操作完成.So这是什么意思?它说mvc应用程序运行在单线程模式，它可以在一个time.So中处理单个请求上面提到的情况永远不会发生。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|361946|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I think it will be never happen,though at beginning I have the same confusion.Think about that if you run your mvc web application in debug mode,then you set a break point in a redirect action .And you give tempdata a value ,then you'll get the tempdate in redirect viewResult and the other view,you will found that the other request never be responsed until the redirect action completed .So what's mean?It said that the mvc application run in single thread mode,it can process a single request in one time.So the scenario above you mentioned can never happen.

When using TempData, my understanding is that it will keep whatever you put in it around for only one request. So when using TempData to retain data across a redirect (in order to use the Post-Request-Get pattern), isn't it possible that some other request from the user could come into the server in between the response sending the redirect and the user's browser requesting the redirected-to page? In which case the get would no longer have the TempData available, correct?

Now, I understand that something like that happening would be very rare, but taking into consideration that the user might have another page open in another tab, and there might be either ajax or timed callback requests occuring on that page, it suddenly doesn't seem all that impossible to me. Is it just generally considered to be too remote to worry about, or am I misunderstanding something?

Edit: To be more specific about the scenario I was asking about.

<ol>
<li>In Tab 1 the user browses to a page
with a post form</li>
<li>In Tab 2 the user browsers to another page on the site that does
ajax callbacks on a timer</li>
<li>In Tab 1, the user posts the form to the server</li>
<li>When the server receives the post, it saves some data in TempData
and sends back a redirect response</li>
<li>In tab 2, the timed ajax callback happens, sending a GET request to the server. The TempData is removed from the session</li>
<li>In tab 1, the browser receives the redirect and issues a GET request</li>
<li>The server processes the GET request and looks for the TempData, but it's not there anymore</li>
</ol>

Is there a possible "race condition" when using Asp.Net MVC TempData across a redirect?

服务器

在使用TempData时，我的理解是它只会为一个请求保留您放在其中的所有内容。因此，当使用TempData跨重定向保留数据时(为了使用Post- request -Get模式)，在发送重定向的响应和请求重定向页面的用户浏览器之间，来自用户的一些其他请求不可能进入服务器吗？在哪种情况下，get将不再有可用的TempDat...

问当通过重定向使用Asp.Net MVC TempData时，是否存在可能的“竞争条件”？
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