1. Tech·Ed North America 2009 11/18/2018 5:14 PM
© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

2. The Future of C# Anders Hejlsberg Technical Fellow Microsoft DTL331
Tech·Ed  North America 2009
11/18/2018 5:14 PM
The Future of C#
Anders Hejlsberg
Technical Fellow
Microsoft
DTL331
© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

3. The Evolution of C# C# 3.0 C# 2.0 C# 1.0 Language Integrated Query
Generics
C# 1.0
Managed Code

4. Trends Declarative Concurrent Dynamic
Move towards more declarative styles of programming
Domain specific, Functional
Resurgence of dynamic programming languages
Meta-programming
Need for better concurrent programming models
Distributed applications
Many-core
Trends cause fusing of ideas from previously distinct disciplines
Functional in mainstream languages
Static typing in dynamic languages
Implicit typing in static languages
Domain specific in every app
HTML, SQL, XAML, XSLT
The classic taxonomies are breaking down
Going forward, mainstream GPLs will be multi-paradigm!

5. Declarative Programming
What
How
Imperative
Declarative

6. Dynamic vs. Static Dynamic Languages Static Languages
Simple and succinct
Implicitly typed
Meta-programming
No compilation
Static Languages
Robust
Performant
Intelligent tools
Better scaling
Dynamic languages have seen a notable resurgence in recent years
In browser, this is perhaps more by necessity than by choice
But even in traditional static language environments…
Interesting to contrast advantages
Dynamic languages
Aim to be simple and succinct
Interactive prompt where you can write one-liners that do useful work
No strong typing to “get in your way”
Strong meta-programming facilities (Eval)
Compilation is implicit—just type your code and run.
Static languages seek to be more robust.
Compile-time errors vs. run-time errors
Strong typing  Statement completion, refactoring, navigation, dependency analysis
Performance better because run-time checks can be avoided
Often scale better to medium and large projects.
In today’s environment, hard to choose
The answer is both!
That’s why they continue to borrow from each other
Interestingly, dynamic language features often have static counterparts
Implicit typing vs. type inference
Extensible objects vs. extension methods

7. Concurrency

8. Co-Evolution

9. The Evolution of C# C# 4.0 C# 3.0 C# 2.0 C# 1.0 Dynamic Programming
Language Integrated Query
C# 2.0
Generics
C# 1.0
Managed Code

10. C# 4.0 Language Innovations
Dynamically Typed Objects
Optional and Named Parameters
Improved COM Interoperability
Co- and Contra-variance

11. .NET Dynamic Programming
IronPython
IronRuby C#
VB.NET
Others…
Dynamic Language Runtime
Expression Trees
Dynamic Dispatch
Call Site Caching
Object Binder
JavaScript Binder
Python Binder
Ruby Binder
COM Binder

12. Dynamically Typed Objects
Calculator calc = GetCalculator();
int sum = calc.Add(10, 20);
object calc = GetCalculator();
Type calcType = calc.GetType();
object res = calcType.InvokeMember("Add",
BindingFlags.InvokeMethod, null,
new object[] { 10, 20 });
int sum = Convert.ToInt32(res);
ScriptObject calc = GetCalculator();
object res = calc.Invoke("Add", 10, 20);
int sum = Convert.ToInt32(res);
Statically typed to be dynamic
dynamic calc = GetCalculator();
int sum = calc.Add(10, 20);
Dynamic conversion
Dynamic method invocation

13. Dynamically Typed Objects
Compile-time type dynamic
Run-time type System.Int32
dynamic x = 1;
dynamic y = "Hello";
dynamic z = new List<int> { 1, 2, 3 };
When operand(s) are dynamic…
Member selection deferred to run-time
At run-time, actual type(s) substituted for dynamic
Static result type of operation is dynamic

14. Dynamically Typed Objects
public static class Math {
public static decimal Abs(decimal value);
public static double Abs(double value);
public static float Abs(float value);
public static int Abs(int value);
public static long Abs(long value);
public static sbyte Abs(sbyte value);
public static short Abs(short value);
... }
Method chosen at compile-time: double Abs(double x)
double x = 1.75;
double y = Math.Abs(x);
Method chosen at run-time: double Abs(double x)
dynamic x = 1.75;
dynamic y = Math.Abs(x);
Method chosen at run-time: int Abs(int x)
dynamic x = 2;
dynamic y = Math.Abs(x);

15. Dynamically Typed Objects
11/18/2018 5:14 PM
demo
If you would like to host your demo on the Virtual Server, please use the myVPC demo slide, not this slide.
Dynamically Typed Objects
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

16. IDynamicObject public abstract class DynamicObject : IDynamicObject {
public virtual object GetMember(GetMemberBinder info);
public virtual object SetMember(SetMemberBinder info, object value);
public virtual object DeleteMember(DeleteMemberBinder info);
public virtual object UnaryOperation(UnaryOperationBinder info);
public virtual object BinaryOperation(BinaryOperationBinder info, object arg);
public virtual object Convert(ConvertBinder info);
public virtual object Invoke(InvokeBinder info, object[] args);
public virtual object InvokeMember(InvokeMemberBinder info, object[] args);
public virtual object CreateInstance(CreateInstanceBinder info, object[] args);
public virtual object GetIndex(GetIndexBinder info, object[] indices);
public virtual object SetIndex(SetIndexBinder info, object[] indices, object value);
public virtual object DeleteIndex(DeleteIndexBinder info, object[] indices);
public MetaObject IDynamicObject.GetMetaObject(); }

17. Implementing IDynamicObject
11/18/2018 5:14 PM
demo
If you would like to host your demo on the Virtual Server, please use the myVPC demo slide, not this slide.
Implementing IDynamicObject
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

18. Optional and Named Parameters
Primary method
public StreamReader OpenTextFile(
string path,
Encoding encoding,
bool detectEncoding,
int bufferSize);
Secondary overloads
public StreamReader OpenTextFile(
string path,
Encoding encoding,
bool detectEncoding);
Encoding encoding);
string path);
Call primary with default values

19. Optional and Named Parameters
Optional parameters
public StreamReader OpenTextFile(
string path,
Encoding encoding = null,
bool detectEncoding = true,
int bufferSize = 1024);
public StreamReader OpenTextFile(
string path,
Encoding encoding,
bool detectEncoding,
int bufferSize);
Named argument
OpenTextFile("foo.txt", Encoding.UTF8);
OpenTextFile("foo.txt", Encoding.UTF8, bufferSize: 4096);
Named arguments can appear in any order
Arguments evaluated in order written
Named arguments must be last
OpenTextFile(
bufferSize: 4096,
path: "foo.txt",
detectEncoding: false);
Non-optional must be specified

20. Improved COM Interoperability
object fileName = "Test.docx";
object missing = System.Reflection.Missing.Value;
doc.SaveAs(ref fileName,
ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing);
doc.SaveAs("Test.docx");

21. Improved COM Interoperability
Automatic object  dynamic mapping
Optional and named parameters
Indexed properties
Optional “ref” modifier
Interop type embedding (“No PIA”)

22. Improved COM interoperability
11/18/2018 5:14 PM
demo
If you would like to host your demo on the Virtual Server, please use the myVPC demo slide, not this slide.
Improved COM interoperability
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

23. Co- and Contra-variance
.NET arrays are co-variant
string[] strings = GetStringArray();
Process(strings);
…but not safely co-variant
void Process(object[] objects) {
objects[0] = "Hello"; // Ok
objects[1] = new Button(); // Exception! }
void Process(object[] objects) { … }
Until now, C# generics have been invariant
List<string> strings = GetStringList();
Process(strings);
C# 4.0 supports safe co- and contra-variance
void Process(IEnumerable<object> objects) { … }
void Process(IEnumerable<object> objects) {
// IEnumerable<T> is read-only and
// therefore safely co-variant }

24. Safe Co- and Contra-variance
public interface IEnumerable<out T> {
IEnumerator<T> GetEnumerator(); }
public interface IEnumerable<T> {
IEnumerator<T> GetEnumerator(); }
out = Co-variant Output positions only
Can be treated as less derived
public interface IEnumerator<out T> {
T Current { get; }
bool MoveNext(); }
public interface IEnumerator<T> {
T Current { get; }
bool MoveNext(); }
IEnumerable<string> strings = GetStrings();
IEnumerable<object> objects = strings;
in = Contra-variant Input positions only
public interface IComparer<T> {
int Compare(T x, T y); }
public interface IComparer<in T> {
int Compare(T x, T y); }
Can be treated as more derived
IComparer<object> objComp = GetComparer();
IComparer<string> strComp = objComp;

25. Variance in C# 4.0 Supported for interface and delegate types
“Statically checked definition-site variance”
Value types are always invariant
IEnumerable<int> is not IEnumerable<object>
Similar to existing rules for arrays
ref and out parameters need invariant type

26. Variance in .NET Framework 4.0
Interfaces
System.Collections.Generic.IEnumerable<out T>
System.Collections.Generic.IEnumerator<out T>
System.Linq.IQueryable<out T>
System.Collections.Generic.IComparer<in T>
System.Collections.Generic.IEqualityComparer<in T>
System.IComparable<in T>
Delegates
System.Func<in T, …, out R>
System.Action<in T, …>
System.Predicate<in T>
System.Comparison<in T>
System.EventHandler<in T>

27. Compiler as a Service Compiler Compiler Meta-programming
Class
Field
public
Foo
private
string X
Meta-programming
Read-Eval-Print Loop
Language
Object Model
DSL Embedding
Compiler
Compiler
Source File
.NET Assembly
Source code
Source code
Source code
Source code

28. question & answer Meet me at Ask-the-Experts in the TLC!
Tuesday 1:15-3:15

29. Resources Required Slide Speakers, www.microsoft.com/teched
TechEd 2009 is not producing
a DVD. Please announce that
attendees can access session
recordings at TechEd Online.
Resources
Sessions On-Demand & Community
Microsoft Certification & Training Resources
Resources for IT Professionals
Resources for Developers
Microsoft Certification and Training Resources

30. Resources C# 4.0 Samples and Whitepaper Video: The Future of C#
Video: The Future of C#
Visual C# Developer Center

31. Related Content
Future Directions for Visual Basic (DTL336) Wed 5/13 | 8:30 AM-9:45 AM | Room 152 Anders Hejlsberg, Jonathan Aneja
Essential LINQ with C# (DTL313) Wed 5/13 | 2:45 PM-4:00 PM | Room 402 Mark Michaelis
How LINQ Works: A Deep Dive into the Visual Basic and C# Implementations (DTL402) Thu 5/14 | 2:45 PM-4:00 PM | Room 515B Jonathan Aneja
Microsoft Visual C# IDE Tips and Tricks (DTL322) Fri 5/15 | 10:45 AM-12:00 PM | Petree Hall C DJ Park
The State of Dynamic Languages on the Microsoft .NET Framework (DTL332)
Fri 5/15 | 1:00 PM-2:15 PM | Room John Lam

32. Complete an evaluation on CommNet and enter to win!
Required Slide
Complete an evaluation on CommNet and enter to win!

33. Required Slide
11/18/2018 5:14 PM
© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.