javascript 版本(asp-append-version)如何在 ASP.NET Core MVC 中工作? [英] How does javascript version (asp-append-version) work in ASP.NET Core MVC?

问题描述

新的MVC似乎不支持动态捆绑(link)，它应该使用 gulp 任务来完成.MVC 支持一些名为 asp-append-version 的新属性，但我没有找到任何关于它如何工作的解释.我怀疑它正在计算文件内容的一些哈希值，甚至在文件更改后更新它.有没有关于它如何工作的文档?

It seems that there is no dynamic bundling supported in the new MVC (link), and it should be done using a gulp task. MVC supports some new attribute called asp-append-version, but I have not found any explanation on how it works. I suspect that it's calculating some hash of the file contents and even updates it after a file change. Is there any documentation on how it works?

我也想知道它是如何检测文件更改的，或者它是否只是在每次 MVC 解析 razor 标记时重新计算哈希.

I am also wondering how it detects the file changes or whether it just recalculates the hash each time the MVC parses razor markup.

推荐答案

可以查看LinkTagHelper 源代码，你会看到它基本上是通过 FileVersionProvider:

if (AppendVersion == true)
{
    EnsureFileVersionProvider();

    if (Href != null)
    {
        output.Attributes[HrefAttributeName].Value = _fileVersionProvider.AddFileVersionToPath(Href);
    }
}

private void EnsureFileVersionProvider()
{
    if (_fileVersionProvider == null)
    {
        _fileVersionProvider = new FileVersionProvider(
                HostingEnvironment.WebRootFileProvider,
                Cache,
                ViewContext.HttpContext.Request.PathBase);
    }
}

FileVersionProvider 将使用 SHA256 算法计算文件内容的哈希值.然后它将对其进行 url 编码并将其添加到查询字符串中，如下所示:

The FileVersionProvider will calculate the hash of the file contents using the SHA256 algorithm. It will then url encode it and add it to the query string as in:

path/to/file?v=B95ZXzHiOuQJzhBoHlSlNyN1_cOjJnz2DFsr-3ZyyJs

仅当文件更改时才会重新计算哈希，因为它已添加到缓存中但具有基于文件观察器的过期触发器:

The hash will be recalculated only when the file changes, as it is added to the cache but with an expiration trigger based on a file watcher:

if (!_cache.TryGetValue(path, out value))
{
    value = QueryHelpers.AddQueryString(path, VersionKey, GetHashForFile(fileInfo));
    var cacheEntryOptions = new MemoryCacheEntryOptions().AddExpirationToken(_fileProvider.Watch(resolvedPath));
    _cache.Set(path, value, cacheEntryOptions);
}

这个watcher由HostingEnvironment.WebRootFileProvider提供，它实现了IFileProvider:

This watcher is provided by HostingEnvironment.WebRootFileProvider, which implements IFileProvider:

//
// Summary:
//     Creates a change trigger with the specified filter.
//
// Parameters:
//   filter:
//     Filter string used to determine what files or folders to monitor. Example: **/*.cs,
//     *.*, subFolder/**/*.cshtml.
//
// Returns:
//     An Microsoft.Framework.Caching.IExpirationTrigger that is triggered when a file
//     matching filter is added, modified or deleted.
IExpirationTrigger Watch(string filter);

注意:您可以通过检查 IMemoryCache 中的值自己查看缓存值:

Note: You can see the cached values yourself by inspecting the values in the IMemoryCache:

//give the link:
<link rel="stylesheet" asp-append-version="true" href="~/css/site.css" />

//You can check the cached version
this.Context.RequestServices.GetRequiredService<IMemoryCache>().Get("/css/site.css")

//Which will show a value like:
/css/site.css?v=B95ZXzHiOuQJzhBoHlSlNyN1_cOjJnz2DFsr-3ZyyJs

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