AuditLog Example

// AuditLog.cs
// ------------------------------------------------------------------
//

using System;
using System.IO;
using System.Text;
using System.Collections.Generic;
using System.Xml;
using System.Xml.Serialization;


namespace Cheeso.Examples
{
    public class Customer
    {
        public string Name    { get; set; }
        public string City    { get; set; }
        public String Country { get; set; }
    }

    public enum Flavor
    {
        Edit,
        Delete
        // more...
    }

    public class AuditRecord<T>
    {
        public AuditRecord() { Stamp = DateTime.Now; }

        [XmlAttribute("action")]
        public Flavor Action  { get; set;}

        [XmlAttribute("stamp")]
        public DateTime Stamp   { get; set;}

        public T Before;
        public T After;
    }

    public class AuditLog<T>
    {
        [XmlIgnore]
        public string StoragePath   { get; set; }

        public int UserID   { get; set; }
        public string LastSaved   { get; set;}
        private List<AuditRecord<T>> _records;

        [XmlArrayItem("Entry")]
        public List<AuditRecord<T>> Records
        {
            get
            {
                if (_records==null)
                    _records = new List<AuditRecord<T>>();
                return _records;
            }

            set
            {
                _records = value;
            }
        }

        public void RecordEdit(T before, T after)
        {
            // a convenience method
            var r = new AuditRecord<T>
                {
                    Before = before,
                    After = after,
                    Action = Flavor.Edit
                };
            Records.Add(r);
        }

        public void RecordDelete(T before)
        {
            // a convenience method
            var r = new AuditRecord<T>
                {
                    Before = before,
                    Action = Flavor.Delete
                };
            Records.Add(r);
        }


        TextWriter GetWriter(bool wantSave)
        {
            if (wantSave)
            {
                var fs = new FileStream(StoragePath, FileMode.Create);
                return new StreamWriter(fs, new UTF8Encoding());
            }
            return Console.Out;
        }

        public void Show()
        {
            SaveShow(false);
        }

        public void Save()
        {
            SaveShow(true);
        }

        protected internal void SaveShow(bool wantSave)
        {
            var writerSettings = new XmlWriterSettings
            {
                OmitXmlDeclaration = true,
                Indent = true
            };

            using (XmlWriter xmlWriter =
                   XmlWriter.Create(GetWriter(wantSave), writerSettings))
            {
                var ns = new XmlSerializerNamespaces();
                ns.Add("", "");
                var ser = new XmlSerializer(this.GetType());
                this.LastSaved = System.DateTime.Now.ToString("yyyy MMM dd HH:mm:ss");
                ser.Serialize(xmlWriter, this, ns);
            }
        }
    }


    public class Program
    {
        public static void Main(string[] args)
        {
            try
            {
                var log = new AuditLog<Customer>();
                var oldCustomer = new Customer
                {
                    Name = "Sheldon", City = "Ipswich", Country = "UK"
                };
                var newCustomer = new Customer
                {
                    Name = "Sheldon", City = "London", Country = "UK"
                };

                log.RecordEdit(oldCustomer, newCustomer);
                log.RecordDelete(newCustomer);

                log.Show();
            }
            catch (System.Exception exc1)
            {
                Console.WriteLine("Exception: {0}", exc1.ToString());
            }
        }
    }
}