DomainService 'XXXService' does not contain any public domain operation?

[namhyuk]

错误提示：DomainService 'UserRegistrationService' does not contain any public domain operations.

主要是想自定义用户注册的Domain Service,从Business app模板拷贝了UserRegistrationService.cs，做了一些小的改动，然后就提示这个错误，我想不起来public domain operation应该是什么样子了。

[EnableClientAccess()]
public class UserRegistrationService : DomainService
{
    public const string DefaultRole = "messenger";

    public CreateUserStatus CreateUser(RegistrationData user, string password)
    {
        if (user == null)
        {
            throw new ArgumentNullException("user");
        }

        if (!Roles.RoleExists(UserRegistrationService.DefaultRole))
        {
            Roles.CreateRole(UserRegistrationService.DefaultRole);
        }

        MembershipCreateStatus createStatus;
        Membership.CreateUser(user.UserName, password, string.Empty, string.Empty, string.Empty, true, null, out createStatus);

        if (createStatus != MembershipCreateStatus.Success)
        {
            return UserRegistrationService.ConvertStatus(createStatus);
        }

        Roles.AddUserToRole(user.UserName, UserRegistrationService.DefaultRole);

        ProfileBase profile = ProfileBase.Create(user.UserName, true);
        profile.SetPropertyValue("FriendlyName", user.FriendlyName);
        profile.Save();

        return CreateUserStatus.Success;
    }
    private static CreateUserStatus ConvertStatus(MembershipCreateStatus createStatus)
    {
        switch (createStatus)
        {
            case MembershipCreateStatus.Success: return CreateUserStatus.Success;
            case MembershipCreateStatus.InvalidUserName: return CreateUserStatus.InvalidUserName;
            case MembershipCreateStatus.InvalidPassword: return CreateUserStatus.InvalidPassword;
            case MembershipCreateStatus.InvalidQuestion: return CreateUserStatus.InvalidQuestion;
            case MembershipCreateStatus.InvalidAnswer: return CreateUserStatus.InvalidAnswer;
            case MembershipCreateStatus.InvalidEmail: return CreateUserStatus.InvalidEmail;
            case MembershipCreateStatus.DuplicateUserName: return CreateUserStatus.DuplicateUserName;
            case MembershipCreateStatus.DuplicateEmail: return CreateUserStatus.DuplicateEmail;
            default: return CreateUserStatus.Failure;
        }
    }
    
    public enum CreateUserStatus
    {
        Success = 0,
        InvalidUserName = 1,
        InvalidPassword = 2,
        InvalidQuestion = 3,
        InvalidAnswer = 4,
        InvalidEmail = 5,
        DuplicateUserName = 6,
        DuplicateEmail = 7,
        Failure = 8,
    }
}

[namhyuk]

Its primary job is to indicate the "RegistrationData" class should be made available to the Silverlight client.
public IEnumerable<RegistrationData> GetUsers()
{
throw new NotSupportedException();
}

[Invoke]
public CreateUserStatus CreateUser(RegistrationData user, string password)
{
...

加上[Invoke]。问题是什么时候加，什么时间不加呢？DomainService CRUD方法不也没加[Invoke]吗？