// This is a work around for the STA thread bug. This will execute the call on a non-sta thread, then return the result
private static bool IsVirtualKnownFolder(IShellItem2 nativeShellItem2)
{
IntPtr pidl = IntPtr.Zero;
try
{
IKnownFolderNative nativeFolder = null;
KnownFoldersSafeNativeMethods.NativeFolderDefinition definition = new KnownFoldersSafeNativeMethods.NativeFolderDefinition();
// We found a bug where the enumeration of shell folders was
// not reliable when called from a STA thread - it would return
// different results the first time vs the other times.
//
// This is a work around. We call FindFolderFromIDList on a
// worker MTA thread instead of the main STA thread.
//
// Ultimately, it would be a very good idea to replace the 'getting shell object' logic
// to get a list of pidl's in 1 step, then look up their information in a 2nd, rather than
// looking them up as we get them. This would replace the need for the work around.
object padlock = new object();
lock (padlock)
{
IntPtr unknown = Marshal.GetIUnknownForObject(nativeShellItem2);
ThreadPool.QueueUserWorkItem(obj =>
{
lock (padlock)
{
pidl = ShellHelper.PidlFromUnknown(unknown);
new KnownFolderManagerClass().FindFolderFromIDList(pidl, out nativeFolder);
if (nativeFolder != null)
{
nativeFolder.GetFolderDefinition(out definition);
}
Monitor.Pulse(padlock);
}
});
Monitor.Wait(padlock);
}
return(nativeFolder != null && definition.category == FolderCategory.Virtual);
}
finally
{
ShellNativeMethods.ILFree(pidl);
}
}
public virtual extern void RegisterFolder(
[In, MarshalAs(UnmanagedType.LPStruct)] Guid knownFolderGuid,
[In] ref KnownFoldersSafeNativeMethods.NativeFolderDefinition knownFolderDefinition);