Selenium how to work with safari Cookies -

i try work selenium , have problem cookies return cookie equals null in method findcookie, google chrome , firefox works good

  public void setcookie(string cookiename, string cookievalue)     {          var cookie = new cookie(cookiename, cookievalue);         driver.manage().cookies.addcookie(cookie);        // driver.manage().cookies.addcookie(new cookie(cookiename, cookievalue, "/"));      }      public string findcookie(string cookiename)     {         var cookienamed = driver.manage().cookies.getcookienamed(cookiename);         if (cookienamed == null)             return null;         return cookienamed.value;     } 

how can works cookie safari?