Microsoft .NET Framework 2.0 Application Development Foundation 翻译系列8(第一章:第四课 类型转换)

'VB

StructureTypeA

PublicValueAsInteger

'Allowsimplicitconversionfromaninteger.

PublicSharedWideningOperatorCType(ByValargAsInteger)AsTypeA

DimresAsNewTypeA

res.Value=arg

Returnres

EndOperator

'Allowsexplicitconversiontoaninteger

PublicSharedNarrowingOperatorCType(ByValargAsTypeA)AsInteger

Returnarg.Value

EndOperator

'Providesstringconversion(avoidsboxing).

PublicOverridesFunctionToString()AsString

ReturnMe.Value.ToString

EndFunction

EndStructure

//C#

structTypeA

{

publicintValue;

//Allowsimplicitconversionfromaninteger.允许将一个integer隐式转换为TypeA

publicstaticimplicitoperatorTypeA(intarg)

{

TypeAres=newTypeA();

res.Value=arg;

returnres;

}

//Allowsexplicitconversiontoaninteger.允许将TypeA显式转换为int

publicstaticexplicitoperatorint(TypeAarg)

{

returnarg.Value;

}

//Providesstringconversion(avoidsboxing).提供字符串转换

publicoverridestringToString()

{

returnthis.Value.ToString();

}

}

'VB

DimaAsTypeA,iAsInteger

'WideningconversionisOKimplicit.

a=42'Ratherthana.Value=42

'Narrowingconversionmustbeexplicit.

i=CInt(a)'Ratherthani=a.Value

'ThissyntaxisOK,too.

i=CType(a,Integer)

Console.WriteLine("a={0},i={0}",a.ToString,i.ToString)

//C#

TypeAa;inti;

//WideningconversionisOKimplicit.放大转换可以是隐式的

a=42;//Ratherthana.Value=42

//Narrowingconversionmustbeexplicit.缩小转换必须是显式的。

i=(int)a;//Ratherthani=a.Value

Console.WriteLine("a={0},i={0}",a.ToString(),i.ToString());

'VB

DimaAsTypeA,bAsBoolean

a=42

'ConvertusingToBoolean.

b=Convert.ToBoolean(a)

Console.WriteLine("a={0},b={1}",a.ToString,b.ToString)

//C#

TypeAa;boolb;

a=42;

//ConvertusingToBoolean.

b=Convert.ToBoolean(a);

Console.WriteLine("a={0},b={1}",a.ToString(),b.ToString());

Lab:SafelyPerformingConversions练习：安全的执行转换

3.'VB

4.Dimi16AsInt16=1

5.Dimi32AsInt32=1

6.DimdbAsDecimal=1

7.

8.//C#

9.Int16i16=1;

10.Int32i32=1;

11.doubledb=1;

13.'VB

14.i16=i32

15.i16=db

16.

17.i32=i16

18.i32=db

19.

20.db=i16

21.db=i32

22.

23.//C#

24.i16=i32;

25.i16=db;

26.

27.i32=i16;

28.i32=db;

29.

30.db=i16;

31.db=i32;