根据URI检测WPF资源是否存在 [英] Detect whether WPF resource exists, based on URI

问题描述

给定 pack://URI，判断已编译资源(例如，使用资源"的构建操作编译的 PNG 图像)是否实际存在于该 URI 中的最佳方法是什么?

Given a pack:// URI, what's the best way to tell whether a compiled resource (e.g. a PNG image, compiled with a Build Action of "Resource") actually exists at that URI?

经过一些磕磕绊绊，我想出了这个代码，它有效但很笨拙:

After some stumbling around, I came up with this code, which works but is clumsy:

private static bool CanLoadResource(Uri uri)
{
    try
    {
        Application.GetResourceStream(uri);
        return true;
    }
    catch (IOException)
    {
        return false;
    }
}

(请注意，Application.GetResources 文档错误 -- 如果资源不正确，则会引发异常找到，而不是像文档错误状态那样返回 null.) (文档已更正，请参阅下面的评论)

(Note that the Application.GetResources documentation is wrong -- it throws an exception if the resource isn't found, rather than returning null like the docs incorrectly state.) (The docs have been corrected, see comments below)

我不喜欢捕捉异常来检测预期的(非异常)结果.此外，我实际上并不想加载流，我只想知道它是否存在.

I don't like catching exceptions to detect an expected (non-exceptional) result. And besides, I don't actually want to load the stream, I just want to know whether it exists.

是否有更好的方法来做到这一点，也许使用较低级别的资源 API —— 理想情况下不实际加载流并且不捕获异常?

Is there a better way to do this, perhaps with lower-level resource APIs -- ideally without actually loading the stream and without catching an exception?

推荐答案

我找到了一个我正在使用的解决方案，它不能直接与包 Uri 一起使用，而是通过资源路径查找资源.话虽如此，这个示例可以很容易地修改以支持包 URI，而不是只需将资源路径添加到 uri 的末尾，该 uri 使用程序集来制定 URI 的基本部分.

I've found a solution that I'm using which doesn't work directly with a pack Uri but instead looks up a resource by it's resource path. That being said, this example could be modified pretty easily to support a pack URI instead by just tacking on the resource path to the end of a uri which uses the Assembly to formulate the base part of the URI.

public static bool ResourceExists(string resourcePath)
{
    var assembly = Assembly.GetExecutingAssembly();

    return ResourceExists(assembly, resourcePath);
}

public static bool ResourceExists(Assembly assembly, string resourcePath)
{
    return GetResourcePaths(assembly)
        .Contains(resourcePath.ToLowerInvariant());
}

public static IEnumerable<object> GetResourcePaths(Assembly assembly)
{
    var culture = System.Threading.Thread.CurrentThread.CurrentCulture;
    var resourceName = assembly.GetName().Name + ".g";
    var resourceManager = new ResourceManager(resourceName, assembly);

    try
    {
        var resourceSet = resourceManager.GetResourceSet(culture, true, true);

        foreach(System.Collections.DictionaryEntry resource in resourceSet)
        {
            yield return resource.Key;
        }
    }
    finally
    {
        resourceManager.ReleaseAllResources();
    }
}

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