Building a Web Message Board using Visual Studio 2008, Part I - The Basic Message Board

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;
using System.Configuration;
using System.Web.Security;
using MessageBoard.Properties;

namespace MessageBoard
{
    /// <summary>
    /// This class is used by the Asp.Net Object Data Source
    /// </summary>
    public static class MessageSource
    {
        private static IMessageProvider _actualMessageProvider = CreateMessageProvider();

        private static IMessageProvider CreateMessageProvider()
        {
            string typeName = ConfigurationManager.AppSettings["MessageBoard-MessageProviderType"];
            Type type = Type.GetType(typeName, true);

            return (IMessageProvider)Activator.CreateInstance(type);
        }
                
        public static IEnumerable<Message> GetRecentMessages(int start, int count)
        {
            return GetRecentMessages(0, start, count);
        }

        public static IEnumerable<Message> GetRecentMessages(int idSince, int start, int count)
        {
            return _actualMessageProvider.GetRecentMessages(idSince, start, count);
        }

        public static int GetMessageCount()
        {
            return _actualMessageProvider.GetMessageCount();
        }

        public static void AddMessage(string subject, string text)
        {
            if (String.IsNullOrEmpty(subject))
                throw new ArgumentException(Resources.SubjectEmpty, "subject");

            if (String.IsNullOrEmpty(text))
                throw new ArgumentException(Resources.TextEmpty, "text");            
            
            //Get the current membership user
            MembershipUser user = Membership.GetUser();
            string postedById = String.Empty;
            string postedBy;

            if (user == null)
            {
                postedBy = Resources.Anonymous;
            }
            else
            {
                postedById = user.ProviderUserKey.ToString();
                postedBy = user.UserName;
            }

            _actualMessageProvider.AddMessage(subject, text, postedBy, postedById, DateTime.Now.ToUniversalTime());
        }

        /// <summary>
        /// Finds a message given an Id and returns a collection of 1 element
        /// </summary>
        /// <param name="id">The id of the message</param>
        /// <returns>A collection of 1 element. A collection is returned so that 
        /// end users can easily data bind
        /// </returns>
        public static IEnumerable<Message> GetMessageById(int id)
        {
            return _actualMessageProvider.GetMessageById(id);
        }
    }
}