Tài liệu Introduction to CSharp 4.0 doc

public abstract class DynamicObject : IDynamicObject{ public virtual object GetMemberGetMemberBinder info; public virtual object SetMemberSetMemberBinder info, object value; public vi

C# 4.0

Dynamic Programming

C# 4.0 Language Innovations

PythonBinder BinderRubyBinderRuby BinderCOMBinderCOM

JavaScriptBinder

JavaScriptBinder

.NET object

object calc = GetCalculator();

Type calcType = calc.GetType();

object res = calcType.InvokeMember("Add",

BindingFlags.InvokeMethod, null,

new object[] { 10, 20 });

int sum = Convert.ToInt32(res);

.NET object

object calc = GetCalculator();

Type calcType = calc.GetType();

object res = calcType.InvokeMember("Add",

BindingFlags.InvokeMethod, null,

new object[] { 10, 20 });

int sum = Convert.ToInt32(res);

Dynamic Language objectScriptObject calc = GetCalculator();

object res = calc.Invoke("Add", 10, 20);int sum = Convert.ToInt32(res);

Dynamic Language object

ScriptObject calc = GetCalculator();

object res = calc.Invoke("Add", 10, 20);

int sum = Convert.ToInt32(res);

Calculator calc = GetCalculator();

int sum = calc.Add(10, 20);

Calculator calc = GetCalculator();

int sum = calc.Add(10, 20);

dynamic calc = GetCalculator();

int sum = calc.Add(10, 20);

dynamic calc = GetCalculator();

int sum = calc.Add(10, 20);

Dynamic method invocation

Dynamic conversion

Dynamic conversion

dynamic calc = GetCalculator();int sum = calc.Add(10, 20);

dynamic calc = GetCalculator();

int sum = calc.Add(10, 20);

dynamic i = 3;Math.Abs(i);

dynamic i = 3;Math.Abs(i);

Under the cover dynamic d = new DynamicObject();

d.Foo();

dynamic d = new DynamicObject();d.Foo();

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();

}

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();

}

Improved COM Interoperability

object -> dynamic mapping

((Excel.Range)xl.Cells[1,1]).Value2 = “ID”;((Excel.Range)xl.Cells[1,1]).Value2 = “ID”;

We need to cast

xl.Cells[1,1].Value2 = “ID”;

Optional and named parameters

xlChart.ChartWizard(cellRange.CurrentRegion, Constants.xl3DBar, PlotBy: Excel.XlRowCol.xlColumns,

written

Arguments evaluated in order

Constants.xl3DBar, Type.Missing, Excel.XlRowCol.xlColumns,

1, 2, false, xlSheet.Name, Type.Missing,

Type.Missing, Type.Missing);

xlChart.ChartWizard(cellRange.CurrentRegion,

Constants.xl3DBar, Type.Missing, Excel.XlRowCol.xlColumns,

1, 2, false, xlSheet.Name, Type.Missing,

Type.Missing, Type.Missing);

public StreamReader OpenTextFile(

Encoding encoding = null,

bool detectEncoding = true,

int bufferSize = 1024);

public StreamReader OpenTextFile(

string path,

Encoding encoding = null,

bool detectEncoding = true,

int bufferSize = 1024);

Optional parameters

Optional parameters

OpenTextFile("foo.txt”);

OpenTextFile("foo.txt”);

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

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

Named argument

Named argument

Optional and named parameters

Optional “ref” modifier

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,

ref missing, ref missing, ref missing,

ref missing, ref missing, ref missing);

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,

ref missing, ref missing, ref missing,

ref missing, ref missing, ref missing);

doc.SaveAs("Test.docx");

Under the cover

void Process(object[] objects) { … }

void Process(object[] objects) { … }

string[] strings = GetStringArray();

void Process(IEnumerable<object> objects) { … }

void Process(IEnumerable<object> objects) { … }

.NET arrays are co-variant

.NET arrays are co-variant

…but not safely

co-variant

…but not safely

co-variant

Until now, C# generics have

been invariant

Until now, C# generics have

been invariant

void Process(IEnumerable<object> objects) {

// IEnumerable<T> is read-only and

// therefore safely co-variant

}

void Process(IEnumerable<object> objects) {

// IEnumerable<T> is read-only and

// therefore safely co-variant

public interface IEnumerable<T>

Output positions only

IEnumerable<string> strings = GetStrings();IEnumerable<object> objects = strings;

IEnumerable<string> strings = GetStrings();

IEnumerable<object> objects = strings;

Can be treated as less derived

Can be treated as less derived

public interface IComparer<T>

IComparer<object> objComp = GetComparer();

IComparer<string> strComp = objComp;

in =

Contra-variant Input positions

only

in =

Contra-variant Input positions

only

Can be treated as more derived

Can be treated as more derived

Variance in C# 4.0

class Base {

public virtual void Foo(int x = 4, int y = 5) {

Console.WriteLine("x:{0}, y:{1}", x, y);

}

}

class Derived : Base {

public override void Foo(int y = 4, int x = 5) {

Console.WriteLine("x:{0}, y:{1}", x, y);

}

}

class Program {

static void Main(string[] args) {

Base b = new Derived();

b.Foo(x: 4, y: 5);

}

}

class Base {

public virtual void Foo(int x = 4, int y = 5) {

Console.WriteLine("x:{0}, y:{1}", x, y);

}

}

class Derived : Base {

public override void Foo(int y = 4, int x = 5) {

Console.WriteLine("x:{0}, y:{1}", x, y);

}

}

class Program {

static void Main(string[] args) {

Base b = new Derived();

Output:

a)x:4, y:5b)x:5, y:4c)x:4, y:4d)x:5, y:5e)None of the above

Output:

a)x:4, y:5b)x:5, y:4c)x:4, y:4d)x:5, y:5e)None of the above

Output:

a)x:4, y:5

b)x:5, y:4

c)x:4, y:4d)x:5, y:5e)None of the above