Question

我创建了一个应用程序，该应用程序使用来自this包的Windows-API-Code-Pack从文件中读取属性。检索属性时出现问题

var width = fileInfo.Properties.GetProperty(SystemProperties.System.Video.FrameWidth).ValueAsObject;

代码在这里中断给我

System.ArgumentException: An item with the same key has already been added.
   at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at Microsoft.WindowsAPICodePack.Shell.PropertySystem.ShellPropertyFactory.GenericCreateShellProperty[T](PropertyKey propKey, T thirdArg)
   at Microsoft.WindowsAPICodePack.Shell.PropertySystem.ShellProperties.GetProperty(PropertyKey key)

通常在PLINQ中调用这部分代码时会发生

.AsParallel().WithDegreeOfParallelism(_maxConcurrentThreads).ForAll(...)

即使将学位设置为1。我该如何解决？

Answer 1

要扩展您现有的答案，将Dictionary切换为ConcurrentDictionary也可以解决问题并消除对锁的需求。

    private static ConcurrentDictionary<int, Func<PropertyKey, ShellPropertyDescription, object, IShellProperty>> _storeCache
        = new ConcurrentDictionary<int, Func<PropertyKey, ShellPropertyDescription, object, IShellProperty>>();
...

    private static IShellProperty GenericCreateShellProperty<T>(PropertyKey propKey, T thirdArg)
    {
       ...

        Func<PropertyKey, ShellPropertyDescription, object, IShellProperty> ctor;
        ctor = _storeCache.GetOrAdd((hash, (key, args) -> {
            Type[] argTypes = { typeof(PropertyKey), typeof(ShellPropertyDescription), args.thirdType };
            return ExpressConstructor(args.type, argTypes);
        }, {thirdType, type});

        return ctor(propKey, propDesc, thirdArg);
    }

Answer 2

遵循stuartd的建议，我可以通过修改包的源代码并在第this code行的第57和62行添加锁来解决此问题，就像这样

lock (_storeCache)
{
    if (!_storeCache.TryGetValue(hash, out ctor))
    {
        Type[] argTypes = { typeof(PropertyKey), typeof(ShellPropertyDescription), thirdType };
        ctor = ExpressConstructor(type, argTypes);
        lock (_storeCache)
            _storeCache.Add(hash, ctor);
    }
}

如何修复Windows API代码包中的ArgumentException？

2 个答案: