Strange how-to behavior

Question

So, I have the following code:

/// <summary> /// The 'Prototype' abstract class /// </summary> abstract class ColorPrototype { public abstract ColorPrototype Clone(); } /// <summary> /// The 'ConcretePrototype' class /// </summary> class Color : ColorPrototype { private int _red; private int _green; private int _blue; // Constructor public Color(int red, int green, int blue) { this._red = red; this._green = green; this._blue = blue; } // Create a shallow copy public override ColorPrototype Clone() { Console.WriteLine( "Cloning color RGB: {0,3},{1,3},{2,3}", _red, _green, _blue); return this.MemberwiseClone() as ColorPrototype; } } /// <summary> /// Prototype manager /// </summary> class ColorManager { private Dictionary<string, ColorPrototype> _colors = new Dictionary<string, ColorPrototype>(); // Indexer public ColorPrototype this[string key] { get { return _colors[key]; } set { _colors.Add(key, value); } } } 

And in the main method, I have:

 ColorManager colormanager = new ColorManager(); // Initialize with standard colors colormanager["red"] = new Color(255, 0, 0); // User clones selected colors ColorPrototype p1 = colormanager["red"].Clone(); bool isColor = p1 is Prototype.Color; Color color1 = p1 as Color; 

My question is why the variable p1 is of type Color ( isColor is true) if in the clone method I passed the result to ColorPrototype ( return this.MemberwiseClone() as ColorPrototype; )?

Link: http://www.dofactory.com/net/prototype-design-pattern

Answer 1

if in the clone method I passed the result to ColorPrototype

Because, even though you drop p1 in ColorPrototype , the execution type of p1 is still of type Color . Reference type casting allows you to view type T as type U , but it does not change the underlying runtime type.

Answer 2

this.MemberwiseClone() returns a Color object. So p1 is actually a Color .

It doesn't matter if you upgrade it to ColorPrototype . Its type of execution is still Color . This is the same as:

 string s = "foo"; object o = s as object; // runtime o type is still string