Transcript C# 4.0 - Dynamic internalsx

Dynamic internals
C# 4.0
Introductions
 Alexandru Ghiondea
 C# Compiler QA
 [email protected]
 http://blogs.msdn.com/alexghi
 What is your programming language of choice?
 Do your apps interop with COM? Do you use
dynamic languages?
 Have you seen C# 4.0 before?
C# 4.0 language features
 Named and Optional parameters
 Omit “ref” for COM calls
 noPIA
 Co&Contra Variance
 Dynamic
Why dynamic?
 There is a lot of interest in accessing the
highly dynamic object model of HTML DOM
 COM is heavily used and the interop code
could be easier to read and write
 Dynamic languages are becoming
increasingly popular
 We need a unified way to work with all of the
above
Architecture
IronPython
IronRuby
C#
VB.NET
Others…
Dynamic Language Runtime
Expression Trees
Object
Binder
JavaScript
Binder
Dynamic Dispatch
Python
Binder
Call Site Caching
Ruby
Binder
COM
Binder
How dynamic works
 We have a new type called dynamic
 Calls on variables of type dynamic are treated
differently by the compiler
 We package extra information about the call
 Calls can be: Method calls, property access, indexer
call, operator call
 There is a C# runtime binder to interpret the
information (at runtime)
 It uses the runtime type for all dynamic arguments
 It uses the compile time type for all other arguments
How dynamic works (2)
COM Binder
CLR
Compile
Run
DLR
Cache
Bind call
Expression
Tree
IronPython
Binder
C# Runtime
Binder
…
IronPython, PowerPoint and C#
DEMO
Under the cover
 What is the Dynamic type?
 There is no dynamic type . There is only object!
 What operations are supported?
 A variable of type dynamic is assumed to support
any kind of operation (method call, property
access, operator call and indexer call)
 How is the information about the call stored?
 Using CallSites objects the compiler packages
data about the call
What does a CallSite
contain?
 Information about the call being made
 What type of call (method call, property, operator,
etc)
 The name of the member
 The context of the call
 The type arguments for the call
 Information about the parameters and return
types
 Is it a constant, is it passed by-ref, etc
Dynamic and CallSites
DEMO
Dynamic FAQ
 When do you go dynamic?
 When the target of the call or any of it’s
parameters are dynamic
 What is the return type of a dynamic call?
 It is dynamic in most cases*
 *What about conversions and constructors?
 They are dispatched at runtime, but their return
type is known at compile time
Dynamic FAQ (2)
 What about private methods?
 Information about the context of call is embedded in
the CallSite allowing the Binder to “do the right thing”
 Calling a method off a non-dynamic target with
dynamic arguments. (c.M(d));
 It works as expected!
 Can dynamic “cross” assembly boundaries?
 Yes, we decorate any dynamic parameter or return
type with a DynamicAttribute
 It works for generic types constructed with dynamic as
well 
Dynamic FAQ (3)
 Can I use Named and Optional with dynamic?
 Yes!
 And also Co & Contra variance
 Where can’t I use dynamic?
 Lambda expressions
 LINQ
 Can’t use dynamic and method groups
 throw or catch statements
Return type, private methods and generics
DEMO
Build you own dynamic object
 It’s simple!
 Implement IDynamicObject
 Derive from DynamicObject
 Implements IDynamicObject
I want to be dynamic!!!
DEMO
Additional Resources
 C# 4.0 Samples and Whitepaper
 http://code.msdn.microsoft.com/csharpfuture
 Visual C# Developer Center
 http://csharp.net
 C# team member’s blogs on dynamic
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http://blogs.msdn.com/cburrows/
http://blogs.msdn.com/samng/
http://blogs.msdn.com/sreekarc/
http://blogs.msdn.com/alexghi/