问PortableDeviceManagerClass在C#中无法初始化

EN

[DllExport]
[return: MarshalAs(UnmanagedType.LPStr)]
public static string getDevices()
{
    try
    {
        var devices = string.Empty;
        var collection = new PortableDeviceCollection();
        collection.Refresh();

        foreach (var device in collection)
        {
            device.Connect();
            if (devices != string.Empty)
            {
                devices += ";";
            }
            devices += device.FriendlyName;
            device.Disconnect();
        }
        return devices;
    }
    catch (Exception e)
    {
        SomeClass.WriteErrorToLogFile(e);
        return "ERROR";
    }
}

public class PortableDeviceCollection : Collection<PortableDevice>
{
    private readonly PortableDeviceApiLib.PortableDeviceManagerClass _deviceManager;

    public  PortableDeviceCollection()
    {
        this._deviceManager = new PortableDeviceApiLib.PortableDeviceManagerClass();
    }

    public bool Refresh()
    {
        this._deviceManager.RefreshDeviceList();
        // Determine how many WPD devices are connected
        var deviceIds = new string[1];
        uint count = 1;
        this._deviceManager.GetDevices(null, ref count);
        if (count > 0)
        {
            // Retrieve the device id for each connected device
            deviceIds = new string[count];
            this._deviceManager.GetDevices(deviceIds, ref count);
            foreach (var deviceId in deviceIds)
            {
                Add(new PortableDevice(deviceId));
            }
            return true;
        }
        else
            return false;
    }
}