Redmine

 public static string[] RedGetAllUsersIds() 

        {

            try

            {

                List<string> UserIds = new List<string>();

                RedmineManager = new RedmineManager(host, apiKey);

                var users = RedmineManager.GetObjects<User>(new NameValueCollection()

                {

                    {RedmineKeys.STATUS, ((int) UserStatus.STATUS_ACTIVE).ToString(CultureInfo.InvariantCulture)}

                });

                foreach (var user in users)

                {   

                    UserIds.Add(user.Id.ToString());

                }

                return UserIds.ToArray();

            }

            catch(Exception ex)

            {

                lastException = ex;

                return null;

            }

        }