Can't install plugin and theme

i want to install some plugin but show

Installation failed: Could not create directory.

that i find some solution add some code to wp-config

//* FTP Settings **/
/** wp-content path */
define('FS_METHOD', 'ftpext');
define('FTP_BASE', '/');
define('FTP_CONTENT_DIR', '/wp-content/');
define('FTP_PLUGIN_DIR', '/wp-content/plugins/');
define('FTP_USER', 'ftpuser');
define('FTP_PASS', 'ftppewd');
define('FTP_HOST', 'domain.com');
define('FTP_SSL', false);

define("FS_METHOD", "direct");
define("FS_CHMOD_DIR", 0777);
define("FS_CHMOD_FILE", 0777);

that the error change to

Installation failed: Unable to connect to the filesystem. Please confirm your credentials

.

i use IIS 8
use ftp client the ftp account has full access right