如果选择allowedTypes，NSOpenPanel不会搜索文件夹

Question

我使用以下代码打开面板，它应该让您能够只选择图像

    openPanel = NSOpenPanel.OpenPanel;
    openPanel.FloatingPanel = true;
    openPanel.CanChooseFiles = true;
    openPanel.AllowsMultipleSelection = true;
    openPanel.CanChooseDirectories = false;
    openPanel.AllowedFileTypes = new string [] { "png", "jpeg", "jpg", "gif" };

    openPanel.BeginSheet (this.View.Window, (obj) => {
        if (obj == 1 && openPanel.Urls != null) {}

当它打开时，我无法搜索文件夹....但如果我启用CanChooseDirectories属性，如果也会搜索文件夹..

如何强制NSOpenPanel搜索文件夹，而不允许选择目录？