A Silverlight application with the WCF RIA Services Class Library

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.DomainServices;
using System.Web.DomainServices.Providers;
using System.Web.Ria;
using Microsoft.Practices.Unity;
using BizApp.Services.Server.Models;

namespace BizApp.Services.Server.DomainServices
{
    /// <summary>
    /// User Registration Domain Service.
    /// </summary>
    /// <remarks>
    /// LinqToSqlMetadataProviderAttribute enables this domain service 
    /// to reference the Linq To SQL generated entities.
    /// </remarks>
    [LinqToSqlMetadataProvider(typeof(AppDatabaseDataContext))]
    [EnableClientAccess]
    public class UserRegistrationService : DomainServiceBase
    {
        // Users will be added to this role by default
        public const string DefaultRole = "Registered User";

        /// <summary>
        /// Gets or sets a repository for the UserAccount entities.
        /// </summary>
        /// <remarks>It is resolved in the DomainServiceFactory. 
        /// IRepository is mapped to the LinqToSqlRepository class in the unity.config.
        /// </remarks>
        [Dependency]
        public IRepository<UserAccount> UserAccountRepository { get; set; }

        /// <summary>
        /// Gets or sets a repository for the UserRole entities.
        /// </summary>
        /// <remarks>It is resolved in the DomainServiceFactory. 
        /// IRepository is mapped to the LinqToSqlRepository class in the unity.config.
        /// </remarks>
        [Dependency]
        public IRepository<UserRole> UserRoleRepository { get; set; }

        /// <summary>
        /// Add a new UserAccount to the database.
        /// </summary>
        /// <param name="user">Registration data.</param>
        /// <returns>UserCreateStatus.</returns>
        /// <exception cref="DomainException" />
        [Invoke]
        public UserCreateStatus AddUser(RegistrationData user)
        {
            if (user == null)
                throw new DomainException("Registration data is empty.");

            if (string.IsNullOrEmpty(user.UserName))
                return UserCreateStatus.InvalidUserName;
            
            if (string.IsNullOrEmpty(user.Email))
                return UserCreateStatus.InvalidEmail;
            
            if (string.IsNullOrEmpty(user.Password))
                return UserCreateStatus.InvalidPassword;

            // Check if an account with this UserName already exists
            var userAccounts = from u in UserAccountRepository.Query()
                               where u.UserName == user.UserName
                               select u;

            if (userAccounts.Count() > 0)
                return UserCreateStatus.DuplicateUserName;

            // Check if an account with this Email already exists
            userAccounts = from u in UserAccountRepository.Query()
                           where u.Email == user.Email
                           select u;

            if (userAccounts.Count() > 0)
                return UserCreateStatus.DuplicateEmail;

            // Get default role ID
            var roles = from r in UserRoleRepository.Query()
                        where r.RoleName == DefaultRole
                        select r;

            UserRole role = roles.FirstOrDefault();

            if(role == null)
                throw new DomainException("Default Role does not exist in the database.");

            UserAccount userAccount = new UserAccount
            {
                UserName = user.UserName,
                FullName = user.FullName,
                Password = user.Password,
                Email = user.Email,
                RoleID = role.ID,
                Created = DateTime.Now
            };

            UserAccountRepository.Add(userAccount);
            UserAccountRepository.SubmitChanges();

            return UserCreateStatus.Success;
        }

        // This is never used but without it RIA Services will complain RegistrationData
        // is not exposed as an entity
        public IEnumerable<RegistrationData> GetUsers()
        {
            throw new NotSupportedException();
        }
    }
}