生成在asp.net图像ETag的？ [英] Generating etags for images in asp.net?

问题描述

在我的网站，用户可以上传所公开展示的图像。当用户上传一个新的形象，它会覆盖旧的图像之一。

On my site, users can upload images that are displayed publicly. When the user uploads a new image, it overwrites one of their old images.

由于图像可能会很大，我希望他们被缓存。然而，当用户上传新图像时，旧的高速缓存的图像，不应使用。

Because the images can be large, I want them to be cached. However, when the user uploads a new image, the old cached images should not be used.

动态影像的来源是这样的：

The source of the dynamic images looks like this:

userImage.ashx?id=f488b864-0a0b-46d9-af4a-a43cd0dcf751&type=micrositePhoto

所以，我可以注入到标题中的ashx的文件的响应，如果我需要。

So I can inject headers into the response in the .ashx file if I need to.

我已经告诉来使用ETag用于此目的，但我不知道如何在asp.net做到这一点。在的.js 和的.css 我的网站上的文件已经有ETag的，但我不知道什么是他们产生。此外，任何内置系统生成的ETag大概不会明白我.ashx的文件是如何工作的。

I've been told to use etags for this purpose, but I don't know how to do this in asp.net. The .js and .css files on my site already have etags, but I don't know what is generating them. Also, any in-built systems to generate etags will probably not understand how my .ashx file works.

我如何为我的网站ETag的，并让这个他们的工作，因为他们咋办？

How do I generate etags for my site, and make it so that they work as they are supposed to?

推荐答案

在我看来，你应该能够做到的，例如：

Looks to me that you should be able to do, for example:

Response.AddHeader("ETag","\"" + Guid.NewGuid().ToString() + "\"");

的ETag必须在括

注意显然，一旦一个ETag返回与它需要在后续请求相同的图像。上面我的code只是一个概念证明。 ：）

NOTE Obviously, once an ETag is returned with an image it needs to be the same on subsequent requests. My code above was just a proof of concept. :)

编辑：是的，只是测试和使用Firebug的响应头确实包含了我创建的GUID证实

Yep, just tested and confirmed using Firebug that the Response headers do contain the Guid that I created.

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