PDC 2008 Experience: Day 1: Session = "The Future of C#"

Co-Evolution of languages: When one feature or capability is added to one language, the feature or ability to have that feature will be placed in the other language.

This is a bit incomplete.  I could not type as fast as slides move.  I will update it when I get the slides.

C# 4.0: Dynamic Programming.

C# 4.0 Language Enhancements

• Dynamically Typed Objects
• Optional and Named Parameters
• Improved COM Interoperability
• Co and Contra variance

Dynamically Typed Objects

Dynamic Language Runtime

• Expression Trees
• Dynamic Dispatch
• Call Site caching

C# and VB.NET will have support for dynamic language.  The Dynamic Runtime will provide the ability to talk to IronPython, Ruby, JavaScript and others.

   1: dynamic calc = new Calculator();

   2: int result = calc.Add(10, 20);

Andres took some Silverlight JavaScript methods and with search and replace made it into C# using the "dynamic" language runtime.

IDynamic Object

TODO: FIX Code; I could not type it fast enough.

   1: using System.Dynamic;

   2:  

   3: public class Bag: DynamicObject

   4: {

   5:     Dictionary<string, object> items = new Dictionary,string, object>();

   6:     public override object GetMember(System.Scripting.ActionsGetMemberAction action, it)

   7:     {

   8:  

   9:     }

  10:  

  11: }

  12:  

  13: class Program

  14: {

  15:     static void Main(string[] args)

  16:     {    

  17:         dynamic x= new Bag();

  18:         x.ID = 12345;

  19:         x.Name = "Lawn Mower";

  20:         x.Price = 795;

  21:         

  22:     }

  23:     private static void WriteBag(dynamic x) {

  24:         Console.WriteLine ();

  25:     }

  26: }

Optional and Named Parameters

Optional Parameters

   1: public StreamReader OpenTextFile(

   2:     string path;

   3:     Encoding = null;

   4:     bool detectEncoding = true;

   5:     int bufferSize = 1024)

Named Arguments

   1: OpenTextFile("foo.txt", Encoding.UTF8, buffersize: 4096);

Improved COM Interoperability

• Automatic object -> dynamic mapping
• Optional and named parameters
• Indexed Properties
• Optional ref "modifier
• Interop type embedding ("NoPIA")

Interop calls do not need to be cast.

TODO: GET Excel Interop sample.

Co and Contra variance

   1: string[] strings = GetStringArray();

   2: Process(strings);

   3:  

   4: ...

   5:  

   6: void Process (string[] input) {...}

can be done using the new C# 4.0 support for safe co- and contra-variance

   1: // Covariant

   2: public interface IEnumerable<out T>

   3: {

   4:     IEnumerable<T> GetEnumerator();

   5: }

   6:  

   7: // Can be treated a less derived

   8: public interface IEnumerable<out t>

   9: {

  10:     T Current get;}

  11:     bool MoveNext();

  12: }

Variance in C#

• Support for interface and delegate types
• "statically checked definitions"
• TODO: Add missing elements

Coming Soon to C#

A new compiler, compiler as a service... Source files -> compiler -> .NET Assembly

This will allow applications to hook into the compiling service for testing, checks, and more.