C# 4.0 - Cairo Code Camp 2010

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Productivity in C# 4.0

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Mohammad Tayseer

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Productivity

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Productivity=

Value

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C#

Object-Oriented Programming

Generics

Expression Trees

Nullable

Lambda Expressions

Anonymous Types

Extension Methods

LINQ

Delegates

Partial Classes

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C# 4.0

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1. Dynamic capabilities

2. Optional and named arguments

3. Co-variant and contra-variant

4. Better COM interoperability

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Dynamic?

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int x = …;x.GetType(); // Safex.SomeMethod(); // Compilation

// error

dynamic d = x;d.GetType(); // Safe

d.SomeMethod(); // Dispatched // at runtime

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x.SomeMethod()

x has SomeMethod

x.TryInvokeMember(“SomeMethod”, …)

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interface IDynamicMetaObjectProvider{

bool TryGetMember(…); bool TrySetMember(…); bool TryDeleteMember(…); bool TryInvoke(…); bool TryInvokeMember(…); bool TryCreateInstance(…); bool TryGetIndex(…); bool TrySetIndex(); bool TryDeleteIndex(…);… }

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PythonBinder

COMBinder

ObjectBinder

Dynamic Language Runtime

IronPython

IronRuby C# VB.NET Others…

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C# 4.0 Dynamic

?

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C# 4.0

Static

Optional dynamic

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When?

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Productivity

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int x = …;

dynamic d = x;

d.SomeMethod(); // Runtime // error

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((MyCompany.MyClient.MyProject.Workflow.Activities.SqlSelect)

this.GetActivityByName(“SqlSelect1”)).RowsAffected > 1

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This is too

complex

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this.SqlSelect1.RowsAffected > 1

Runtime Lookup Recursive

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this.SqlSelect1.RowsAffected > 1

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dynamic x = …;x.GetType();x.Property1 = x.Property2;x[“1”] = x[“value 2”];x(1, 2, 3)x++;

x.ExtensionMethod() // Runtime error

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Dynamic Dispatch

Demo

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Named & optional

parameters

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chart.ChartWizard(range.CurrentRegion,MissingValue,MissingValue,MissingValue,MissingValue,MissingValue,MissingValue,"Memory Usage in " + Environment.MachineName,MissingValue,MissingValue,MissingValue);

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chart.ChartWizard(range.CurrentRegion, // SourceMissingValue, // GalleryMissingValue, // FormatMissingValue, // PlotByMissingValue, // CategoryLabelsMissingValue, // SeriesLabelsMissingValue, // HasLegend// Title"Memory Usage in " + Environment.MachineName,MissingValue, // CategoryTitleMissingValue, // ValueTitleMissingValue); // ExtraTitle

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Strongly-typednamed

parameters

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chart.ChartWizard(Source: range.CurrentRegion,Gallery: MissingValue,Format: MissingValue,PlotBy: MissingValue,CategoryLabels: MissingValue,SeriesLabels: MissingValue,HasLegend: MissingValue,Title: "Memory Usage in " + Environment.MachineName,CategoryTitle: MissingValue,ValueTitle: MissingValue,ExtraTitle: MissingValue);

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Optional parameters

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chart.ChartWizard(Source: range.CurrentRegion,Title: "Memory Usage in " + Environment.MachineName);

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public void ChartWizard(Source = null,Gallery = null,Format = null,PlotBy = null,CategoryLabels = null,SeriesLabels = null,HasLegend = null,Title = “”,CategoryTitle = null,ValueTitle = null,ExtraTitle = null)

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Co-variance & Contra-variance

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Back to Basics

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Lion is-a Animal

Camel is-a Animal

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public static string CleanAnimal(Animal a)

{…}

CleanAnimal(camel);CleanAnimal(lion);

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Thus

Stack<Lion>is-a

Stack<Animal>

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No

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public static string CleanAll(Stack<Animal> animals)

{ … }

Stack<Lion> lions = { … };

CleanAll(lions);

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public static string CleanAll(Stack<Animal> animals)

{animals.Push(new Camel());

…}

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Stack<Lion> is-not

Stack<Animal>

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IEnumerable<Lion> should-be

IEnumerable<Animal>

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IEnumerable<Lion>,IEnumerator<Lion>

are read-only

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Only in C# 4

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interface IEnumerator<out T>// T only in output position{T Current { get; }}

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interface IEnumerable<out T>{IEnumerator<T> GetEnumerator();}

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Co-variance

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Now Contra-variance

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interface IPushable<in T>{void Push(T element);}

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IPushable<Animal>is-a

IPushable<Lion>

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IPushable<Lion> lions = animals;lions.Push(new Lion());

IPushable<Camel> camels = animals;

camels.Push(new Camel());

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Limitations

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1.Interfaces

2.Delegates

3.Reference types

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Co-variance & Contra-variance

Demo

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BetterCOM

Interoperability

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1. Dynamic

2. Optional & named params

3. No PIA

4. Omitting ref

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Demos

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twitter.com/m_tayseer

http://spellcoder.com/blogs/tayseer

[email protected]

http://spellcoder.com/bogs/tayseer

C# 4.0 - Cairo Code Camp 2010

Technology

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