Can anybody give a good example of what to use generic classes for?
public class CatFactory
{
  public Cat CreateCat()
  {
    return new Cat();
  }
}

public class Factory<T> where T : new()
{
  public T Create()
  {
    return new T();
  }
}

// interface for included tools to build your furniture
public interface IToolKit {
    string[] GetTools();
}

// interface for included parts for your furniture
public interface IParts {
    string[] GetParts();
}

// represents a generic base class for IKEA furniture kit
public abstract class IkeaKit<TContents> where TContents : IToolKit, IParts, new() {
    public abstract string Title {
        get;
    }

    public abstract string Colour {
        get;
    }

    public void GetInventory() {
        // generic constraint new() lets me do this
        var contents = new TContents();
        foreach (string tool in contents.GetTools()) {
            Console.WriteLine("Tool: {0}", tool);
        }
        foreach (string part in contents.GetParts()) {
            Console.WriteLine("Part: {0}", part);
        }
    }
}

// describes a chair
public class Chair : IToolKit, IParts {
    public string[] GetTools() {
        return new string[] { "Screwdriver", "Allen Key" };
    }

    public string[] GetParts() {
        return new string[] {
            "leg", "leg", "leg", "seat", "back", "bag of screws" };
    }
}

// describes a chair kit call "Fnood" which is cyan in colour.
public class Fnood : IkeaKit<Chair> {
    public override string Title {
        get { return "Fnood"; }
    }

    public override string Colour {
        get { return "Cyan"; }
    }
}

public class Snoolma : IkeaKit<Chair> {
    public override string Title {
        get { return "Snoolma "; }
    }

    public override string Colour {
        get { return "Orange"; }
    }
}

var fnood = new Fnood();
fnood.GetInventory(); // print out tools and components for a fnood chair!