C# 4.0 and .NET 4.0

C# 4.0 and .NET 4.0
Buu Nguyen, MVP (ASP.NET)
www.buunguyen.net/blog
buunguyen@kms-technology.com
Microsoft Confidential
1

Agenda
Optional and Named Parameters
Covariance and Contravariance
Dynamic Binding
Threading with Task API
Task Parallel Library (TPL)
PLINQ

Optional and Named Parameters

?Quiz
What are 2 issues of this API?

Covariance and Contravariance

?Quiz
What is wrong with this code?

Covariance Defined
Let’s say S is subtype of B and GT is a generic type
GT<S> behaves like subtype of GT on assignment compatibility, i.e.
GT<S> s = …
GT b = s;
GT<S> s = (GT<S>)b;
Safe only when GT doesn’t expose members “receiving” T as input (aka input-safe)
7

?Quiz
What is wrong with this code?

Contravariance Defined
Let’s say S is subtype of B and GT is a generic type
GT behaves like subtype of GT<S> on assignment compatibility, i.e.
GT b = …
GT<S> s = b;
GT b = (GT)s;
Safe only when GT doesn’t expose members “returning” T as output (aka output-safe)
9

Dynamic Binding

?Quiz
Write a method that prints out the Name property of an anonymous object returned by another method

Dynamic binding means…
use runtime type for all bindings

?Quiz
A method summing Length properties of all parameters, regardless of actual type

?Quiz
How to builds C# objects that behave like JavaScript objects, i.e. members can be added at any time?

?Quiz
Write a class whose objects can invoke static methods of any particular type
Bonus #1: include non-public static methods
Bonus #2: ignore case

?Quiz
Write a class whose objects can be used as result-caching proxy for the method invocation of any other object

Task Parallel Library (TPL) & PLINQ

?Quiz
Write a method calculating Fibonacci number using a thread in thread-pool and returning result to caller

Task Parallelism Features
Wait on tasks
Support parent-child relationship
Exception handling
Cancelling tasks
Continuation
Execute one task after another
19

?Quiz
Write 3 methods:
Calculate some known Fibonacci numbers
Calculate Fibonacci numbers for a range
Calculate Fibonacci numbers for a list of specified indexes
Each calculation must take place in a thread in thread-pool

Parallel Class
Assign delegates to a handful of Task instances, not one-to-one mapping

?Quiz
Write a method which calculate some specified Fibonacci numbers and return the sum of them to the caller

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C# 4.0 and .NET 4.0

by Buu Nguyen on Apr 18, 2010

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C# 4.0 and .NET 4.0 — Presentation Transcript