How to fix ArgumentException in Windows-API-Code-Pack?

Question

I've created an application that reads properties from files using the Windows-API-Code-Pack from this package. I'm having an issue when retrieving properties

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

The code breaks here giving me

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)

This happens mostly when calling this portion of a code in a PLINQ

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

even if the degree is set to 1. How can I solve it?

Answer 1

To extend on your existing answer, switching the Dictionary to a ConcurrentDictionary would also solve the problem and remove the need for locks.

    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

Following stuartd suggestion I was able to solve this issue by modifying the source code of the package and adding locks in this code at lines 57 and 62, like this

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);
    }
}