ATMLCommonLibrary.controls.ATMLPreviewPanel.GetPreviewHandlerGUID C# (CSharp) Method

        private Guid GetPreviewHandlerGUID( string filename )
        {
            RegistryKey ext = Registry.ClassesRoot.OpenSubKey( Path.GetExtension( filename ) );
            if (ext != null)
            {
                RegistryKey test = ext.OpenSubKey( "shellex\\{8895b1c6-b41f-4c1c-a562-0d564250836f}" );
                if (test != null) return new Guid( Convert.ToString( test.GetValue( null ) ) );

                string className = Convert.ToString( ext.GetValue( null ) );
                if (className != null)
                {
                    test =
                        Registry.ClassesRoot.OpenSubKey( className + "\\shellex\\{8895b1c6-b41f-4c1c-a562-0d564250836f}" );
                    if (test != null) return new Guid( Convert.ToString( test.GetValue( null ) ) );
                }
            }
            return Guid.Empty;
        }