Now more dynamic than ever

The dynamic keyword was introduced in C# 4 and I remember reading about it back then. Most of the articles (like this one) highlighted using it for late binding of method calls. Useful for calling external libraries in a different language or interfacing with old COM code but not something I would normally need in managed C# land.

Well the other day as I was reading about the Visitor pattern in C# I came across this article (Farewell Visitor) which used dynamic dispatch to simplify the visitor code. Very neat use of dynamic to essentially dynamically cast a variable to the underlying object type before calling a matching overridden method.

To see a quick example of this in action past the following code in LinqPad and check out the results.

void Main() {    var shapes = new List<shape>();  shapes.Add(new Shape());  shapes.Add(new Circle());  shapes.Add(new Square());     // Only the Shape method gets called each time  foreach (var element in shapes) {   PrintShape(element);  }     Console.WriteLine();     // Using dynamic the matching object method gets called  foreach (dynamic element in shapes) {   PrintShape(element);  } }   public void PrintShape(Shape shape) {  Console.WriteLine("I am a Shape"); }   public void PrintShape(Circle circle) {  Console.WriteLine("I am a Circle"); }   public void PrintShape(Square square) {  Console.WriteLine("I am a Square"); }   // Simple shape and two subclasses public class Shape { }   public class Circle : Shape { }   public class Square : Shape { }   </shape>