/// <summary>
/// 退出登录的公共方法
/// </summary>
/// <param name="userName">要退出登录的用户名</param>
public void Logout(string userName)
{
if (StateProvider == null)
{
throw new ArgumentNullException("没有提供StateProvider，请提供实现了IStateProvider接口的登录提供程序。");
}
if (!userName.IsEmpty())
{
StateProvider.Logout(userName);
FormsAuthentication.SignOut();
AppUser user = UserManager.GetByName(userName);
if (user != null)
{
user.IsOnline = false;
}
}
}