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.Configuration;

namespace MessageBoard.DataAccess.Linq
{
    public class LinqMessageProvider : IMessageProvider
    {
        #region IMessageSource Members

        public IEnumerable<Message> GetRecentMessages(int lastId, int start, int count)
        {
            using (MessageBoardDataContext context = CreateDataContext())
            {
                var messages = from m in context.Messages
                               where m.Id > lastId
                               orderby m.DatePosted descending
                               select m.Freeze();
                
                var messagesInRange = messages.Skip(start).Take(count);
                
                return messagesInRange.ToList();
            }
         }

        public int GetMessageCount()
        {
            using(MessageBoardDataContext context = CreateDataContext())
                return context.Messages.Count();
        }

        private static MessageBoardDataContext CreateDataContext()
        {
            MessageBoardDataContext context = new MessageBoardDataContext();
            context.ObjectTrackingEnabled = false;

            return context;
        }

        public int AddMessage(string subject, string text, string postedBy, string postedById, DateTime datePosted)
        {
            using (MessageBoardDataContext context = CreateDataContext())
            {
                context.ObjectTrackingEnabled = true;

                Message message = new Message();
                message.Subject = subject;
                message.Text = text;
                message.PostedBy = postedBy;
                message.PostedById = postedById;
                message.DatePosted = datePosted;
                context.Messages.InsertOnSubmit(message);

                context.SubmitChanges();

                //After calling submit changes the Id is automatically updated
                return message.Id;
            }
        }

        public IEnumerable<Message> GetMessageById(int id)
        {
            using (MessageBoardDataContext context = CreateDataContext())
            {
                return (from m in context.Messages
                       where m.Id == id
                       select m).ToList();
            }
        }
        
        #endregion
    }
}