// WorkItem implicitly inherits from Object class
public class WorkItem
{
    private static int nextID;
    protected int ID { get; set; }
    protected TimeSpan jobLength { get; set; }
    protected string Title { get; set; }
    protected string Description { get; set; }
    // Default constructor
    public WorkItem() 
    {
        ID = 0;
        Title = "Default title";
        Description = "Default description.";
        jobLength = new TimeSpan();
    }
    // Static constructor for static member.
    static WorkItem()
    {
        nextID = 0;
    }
    // Instance constructor.
    public WorkItem( string title, string desc, TimeSpan joblen)
    {
        this.ID = GetNextID();                
        this.Title = title;
        this.Description = desc;
        this.jobLength = joblen;
    }
    protected int GetNextID()
    {
       return ++nextID;
    }
    public void Update(string title, TimeSpan joblen)
    {
        this.Title = title;
        this.jobLength = joblen;
    }

    // Virtual method override.
    public override string ToString()
    {
        return String.Format("{0} - {1}", this.ID, this.Title); 
    }
}

// ChangeRequest derives from WorkItem and adds two of its own members.
public class ChangeRequest : WorkItem
{
    protected int originalItemID {get; set;}
    public ChangeRequest() { }
    public ChangeRequest(string title, string desc, TimeSpan jobLen, int originalID)
    {
        this.ID = GetNextID();
        this.Title = title;
        this.Description = desc;
        this.jobLength = jobLen;
        this.originalItemID = originalID;
    }
}

class Program
{
    static void Main()
    {
        WorkItem item = new WorkItem(                                
                        "Fix Bugs", 
                        "Fix all bugs in my source code branch",
                        new TimeSpan(3, 4, 0, 0));

        ChangeRequest change = new ChangeRequest("Change design of base class",
                                                 "Add members to base class",
                                                 new TimeSpan(4, 0, 0),
                                                 1);

        Console.WriteLine(item.ToString());

        // ChangeRequest inherits WorkItem's override of ToString
        Console.WriteLine(change.ToString()); 

        // Keep the console open in debug mode.
        Console.WriteLine("Press any key to exit.");
        Console.ReadKey();
    }
}
/* Output:
    1 - Fix Bugs
    2 - Change design of base class
*/