Building a Web Message Board using Visual Studio 2008 Part II - Posting messages using Microsoft Word

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.Serialization;
using MessageBoard.Properties;

namespace MessageBoard
{
    /// <summary>
    /// Represents a message in the message board
    /// </summary>
    [DataContract]
    public class Message
    {
        public Message()
        {
        }
        
        public Message(int id, string subject, string text, string postedBy, string postedById, DateTime postedDate)
        {
            this.Id = id;
            this.Subject = subject;
            this.Text = text;
            this.PostedBy = postedBy;
            this.PostedById = postedById;
            this.DatePosted = postedDate;
            this.Frozen = true;
        }

        private int _id;

        [DataMember]
        public int Id
        {
            get { return _id; }
            set { CheckImmutable(); _id = value; }
        }

        private string _subject;

        [DataMember]
        public string Subject
        {
            get { return _subject; }
            set { CheckImmutable(); _subject = value; }
        }

        private string _text;

        [DataMember]
        public string Text
        {
            get { return _text; }
            set { CheckImmutable(); _text = value; }
        }

        private string _postedBy;

        [DataMember]
        public string PostedBy
        {
            get { return _postedBy; }
            set { CheckImmutable(); _postedBy = value; }
        }

        private string _postedById;

        [DataMember]
        public string PostedById
        {
            get { return _postedById; }
            set { CheckImmutable(); _postedById = value; }
        }

        private DateTime _datePosted;

        [DataMember]
        public DateTime DatePosted
        {
            get { return _datePosted; }
            set { CheckImmutable(); _datePosted = value; }
        }

        private void CheckImmutable()
        {
            if (Frozen)
                throw new InvalidOperationException(Resources.ObjectFrozen);
        }

        public bool Frozen { get; private set; }

        public Message Freeze()
        {
            this.Frozen = true;
            return this;
        }
    }
}