C# 3.0 Feature Break Down

These are the new language features that I found being talked about;

  • Better Type Inferencing including the use of “var’ key word which macro-ishly rewrites to the type of object you assign to it. This is also the case with Arrays which now do not need explicit type declarations
    • var x = 42;
    • var arr = new[]{“This”, “is”, “a”, “string”, “array”};
  • Keyword Arguments in Constructors
    • new Point( X = 3, Y = 4)
    • X, and Y have a syntax to declare them similar to public accessors
    • //Due to Better Type inferencing we can elide Point
      var r = new Rectangle {
      P1 = { X = 0, Y = 1 },
      P2 = { X = 2, Y = 3 }
  • Seems to have anonymous types / classes with an easy syntax
    • var x = new (X = 3, Y = 4)
    • var p1 = new { Name = "Lawnmower", Price = 495.00 };
      var p2 = new { Name = "Shovel", Price = 26.95 };
      p1 = p2; //These are of the same anonymous type
  • Opening base classes to provide functionality (a bit, you still cannot get to non public members on that class.)
    • namespace Extender{
      public static class XMLUtil {
      public static string ToXML(this Point pt) {
      // stuff
    • Notice that our first parameter must be a type definition for the object we are wanting to extend.

  • Lambda expressions which in C# 3.0 seem to be mostly better syntax for anonymous delegates with outer variable capture(sic). For some reason they thought that the ADwOVC were a little verbose for the task at hand, and were not quite enough like LISP lambdas.
    • x => x + 1 // Implicitly typed, expression body
    • x => { return x + 1; } // Implicitly typed, statement body
    • (int x) => x + 1 // Explicitly typed, expression body
    • (int x) => { return x + 1; } // Explicitly typed, statement body
    • (x, y) => x * y // Multiple parameters
    • () => Console.WriteLine() // No parameters(Yay Thunk!)
  • Query Expression / LINQ: This is a big, so I am only going to cover it briefly. The goal of this is to allow set processing language in your C# program. It will convert a “Query Expression” into a series of function calls that will operate on a set of data. There is a ton more information about this out on the web if it piques your interest.
    • from c in customers
      from o in c.Orders
      orderby o.Total descending
      select new { c.Name, o.OrderID, o.Total }
    • from c in customers
      join o in orders on c.CustomerID equals o.CustomerID
      join d in details on o.OrderID equals d.OrderID
      join p in products on d.ProductID equals p.ProductID
      select new { c.Name, o.OrderDate, p.ProductName }
  • Expression Trees (from the spec): permit lambda expressions to be represented as data structures instead of executable code. Expression trees are efficient in-memory data representations of lambda expressions and make the structure of the expression transparent and explicit. While this certainly sounds interesting I wish they would have spent more than a paragraph on it in the language spec. My guess is that this is mostly in there to support what LINQ is doing more than that this was intended for end user use much. It is possible though that this would allow for macros expressed as operations on an Expression Tree. It also seems to backdoor in runtime evaluation.

The final result is that C# 3 is still static all over the damn place, but hey… they are working on it. Maybe version 4 will have a regular old eval function (hehehe)

C# 3.0 Language Spec
Extremely long article that I skimmed through and stole an example out of

Also … I started this cool post war on reddit.

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