EnvDTE 循环访问解决方案中的子文件夹

VS解决方案中具有以下结构：

现在，我想获取对"目录"文件夹的引用并将其存储在变量中：

        //Solution_Name
        //    ConfigurationObjects
        //        Catalogs
        //        Documents
    foreach (Project item1 in AttachedSolution.Projects)
    {
        if (item1.Kind == ProjectKinds.vsProjectKindSolutionFolder)
        {
            if (item1.Name == "ConfigurationObjects")
            {
                SolutionFolder catalogBaseFolder = (SolutionFolder)item1.Object;
                foreach (ProjectItem item2 in item1.ProjectItems)
                {
                    if ( item2.Name == "Catalogs")
                    {
                        this.CatalogObjectsFolder = (SolutionFolder)item2;
                    // raises error here: Unable to cast COM object of type                   
                    //'System.__ComObject' 
                    //to interface type 'EnvDTE80.SolutionFolder'.
                    };
                };
            };
        };
    };

感谢您的帮助。