blocks|key|1240623|text|只有当该功能包含在web服务器中时，这是非常不可能的。所以没有，抱歉。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1240624|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|$]]

Only if that functionality is included in the web server, and that's pretty unlikely. So no, sorry.

blocks|key|3605554|text|对于任何给定的页面，都不是。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3605555|但是，如果您编写了一个工具来根据时间戳或某种ID给出差异，那么是的。这不是任何标准的东西。您必须使用联合为页面创建一个提要，或者创建一个web服务来满足需求。当然，您必须控制您想要监控的web服务器，这对您来说可能并非如此。|3605556|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Not for any given page, no.

But if you wrote a facility to give you the differences based on a timestamp or some kind of ID, then yes. This isn't anything standard. You'd have to create a feed for the page using syndication, or create a web service to satisfy the need. Of course, you have to be in control of the web server you want to monitor, which may not be the case for you.

blocks|key|1246983|text|简短的回答是，不。长长的答案是，如果HTML在版本控制中，并且您编写了一些服务器端代码，该代码在给定特定版本号的情况下给出了当前版本和指定版本之间的差异，那么是的。如果HTML不在版本控制中，并且您只想将您的版本与当前版本进行比较，那么您需要下载当前版本以便在客户端进行比较，或者将您的版本上传到服务器并让服务器进行比较--然后将差异发送回去。显然，让客户重新下载新版本会更有效率。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1246984|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|$]]

The short answer is, no. The long answer is that if the HTML is in version control and you write some server side code that, given a particular version number, gives you the diff between the current version and the specified version, yes. If the HTML isn't in version control and you just want to compare your version to the current version, then either you need to download the current version to do the comparison on the client or upload your version to the server and have it do the comparison -- and send the difference back. Obviously, it's more efficient just to have your client re-download the new version.

blocks|key|5074130|text|设置HttpWebRequest的IfModifiedSince属性。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5074131|这不会给你‘增量’，但如果页面根本没有被修改，它会回复301。|5074132|entityMap^0|2|E|H|F|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

Set <code>IfModifiedSince</code> property of <code>HttpWebRequest</code>.

This won't give you 'delta', but will reply with 301 if the page was not modified at all.

blocks|key|1289351|text|您使用的是旧版本，服务器使用的是新版本。你怎么能在不知道有什么变化的情况下只下载增量呢？在不知道您的旧版本的情况下，服务器如何交付增量？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1289352|显然，没有办法下载整个页面。或者将旧版本上传到服务器(假设服务器有一个允许这样做的服务)，但这只会增加流量。|1289353|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

You have the old version and the server has the new version. How could you download just the delta without knowing what has been changed? How could the server deliver the delta without knowing which old version you have?

Obviously, there is no way around downloading the entire page. Or uploading the old version to the server (assuming the server has a service that allows that), but that would only increase the traffic.

blocks|key|3605716|text|像我之前的其他答案一样，没有办法绕过下载。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3605717|但是，您不能通过为每个页面修订创建散列并将当前散列与新散列进行比较来解析相同的html。然后，您将使用diff算法来仅提取“增量”信息。我认为大多数现代爬行器都是这样做的。|3605718|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Like the other answers before me, There is no way to get around the download.

You can however not parse the html if it the same by creating a hash for each page revision and comparing the current hash with the new hash. Then you would use a diff algorithm to extract only the 'delta' information. I think most modern crawlers do something along these lines.

blocks|key|3605821|text|如果旧版本保留在web服务器上，并且当您请求增量时，您发送了一个“版本号”或已有版本的修改日期，理论上服务器可以比较页面并仅发送差异。但两个副本必须在一台机器上，任何人都能知道其中的区别。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3605822|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|$]]

If the older versions were kept on the web server, and when you requested the delta, you sent a 'version number' or a modified date for the version that you have, theoretically the server could diff the page and send only the difference. But both copies have to be on one machine for anybody to know what the difference is.

blocks|key|1240808|text|您可以使用HttpWebRequest类的AddRange方法。使用此选项，您可以指定要下载的资源的字节范围。这也用于继续中断的http下载。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1240809|这不是增量，但如果您只加载更改的部分，则可以减少流量。|1240810|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

You could use the AddRange method of the HttpWebRequest Class.
With this you can specify a byte range of the ressource you want to download.
This is also used to continue interrupted http downloads.

This is no delta but you can decrease traffic if you only load the parts that change.

I'm using C# + HttpWebRequest.
I have an HTML page I need to frequently check for updates.
Assuming I already have an older version of the HTML page (in a string for example), is there any way to download ONLY the "delta", or modified portion of the page, without downloading the entire page itself and comparing it to the older version?

C# - how to download only the modified part of an HTML

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我使用的是C# + HttpWebRequest。我有一个HTML页面，我需要经常检查更新。假设我已经有了一个旧版本的HTML页面(例如在字符串中)，有没有办法只下载页面的“增量”或修改部分，而不下载整个页面本身并将其与旧版本进行比较？

问C# -如何只下载修改过的部分
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