AS

string s = someObject as string;

if (s != null)

{

// someObject is a string.

} 備註

as 運算符類似於強制轉換操作；但是，如果轉換不可行，as 會返回 null 而不是引發異常。更嚴格地說，這種形式的表達式

expression as type等效於

expression is type ? (type)expression : (type)null只是 expression 只被計算一次。

注意，as 運算符只執行引用轉換和裝箱轉換。as 運算符無法執行其他轉換，如用戶定義的轉換，這類轉換應使用 cast 表達式來執行。

示例

// cs_keyword_as.cs

// The as operator.

using System;

class Class1

{

}

class Class2

{

}

class MainClass

{

static void Main()

{

object[] objArray = new object[6];

objArray[0] = new Class1();

objArray[1] = new Class2();

objArray[2] = "hello";

objArray[3] = 123;

objArray[4] = 123.4;

objArray[5] = null;

for (int i = 0; i < objArray.Length; ++i)

{

string s = objArray as string;

Console.Write(":", i);

if (s != null)

{

Console.WriteLine("'" + s + "'");

}

else

{

Console.WriteLine("not a string");

}

}

}

}輸出

0:not a string

1:not a string

2:'hello'

3:not a string

4:not a string

5:not a string C# 語言規範

有關更多信息，請參見 C# 語言規範中的以下各章節：

6 轉換

7.9.10 as 運算符

Graphics繪圖

JavaScript Code複製內容到剪貼板

backLayer=newLSprite();

addChild(backLayer);

//畫一圓

backLayer.graphics.drawRect(1,"black",[20,20,150,20],true,"#cccccc");

//畫一個矩形

backLayer.graphics.drawArc(2,"black",[100,100,50,0,2*Math.PI,false],true,"#FF0000");

//畫一條線

backLayer.graphics.drawLine(2,"#FF0000",[200,20,100,50]);

1.

backLayer=newLSprite();

2.

addChild(backLayer);

3.

//畫一圓

4.

backLayer.graphics.drawRect(1,"black",[20,20,150,20],true,"#cccccc");

5.

//畫一個矩形

6.

backLayer.graphics.drawArc(2,"black",[100,100,50,0,2*Math.PI,false],true,"#FF0000");

7.

//畫一條線

8.

backLayer.graphics.drawLine(2,"#FF0000",[200,20,100,50]);