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C#引用托管對(duì)象概述
學(xué)習(xí)C#語(yǔ)言時(shí)，經(jīng)常會(huì)遇到C#引用托管對(duì)象問(wèn)題，這里將介紹C#引用托管對(duì)象問(wèn)題的解決方法。
如果在調(diào)用平臺(tái) invoke 后的任何位置都未C#引用托管對(duì)象，則垃圾回收器可能將完成該托管對(duì)象。這將釋放資源并使句柄無(wú)效，從而導(dǎo)致平臺(tái)invoke 調(diào)用失敗。用 HandleRef 包裝句柄可保證在平臺(tái)invoke 調(diào)用完成前，不對(duì)托管對(duì)象進(jìn)行垃圾回收。
C#引用托管對(duì)象例如下面：
- FileStream fs = new FileStream( "a.txt", FileMode.Open );
- StringBuilder buffer = new StringBuilder( 5 );
- int read = 0;
- ReadFile(fs.Handle, buffer, 5, out read, 0 );
- //調(diào)用Win API中的ReadFile函數(shù)
由于fs是托管對(duì)象，所以有可能在平臺(tái)調(diào)用還未完成時(shí)候被垃圾回收站回收。將文件流的句柄用HandleRef包裝后，就能避免被垃圾站回收:
- [ DllImport( "Kernel32.dll" )]
- public static extern bool ReadFile(
- HandleRef hndRef,
- StringBuilder buffer,
- int numberOfBytesToRead,
- out int numberOfBytesRead,
- ref Overlapped flag );
- ......
- ......
- FileStream fs = new FileStream( "HandleRef.txt", FileMode.Open );
- HandleRef hr = new HandleRef( fs, fs.Handle );
- StringBuilder buffer = new StringBuilder( 5 );
- int read = 0;
- // platform invoke will hold reference to HandleRef until call ends
- ReadFile( hr, buffer, 5, out read, 0 );
文章名稱(chēng)：C#引用托管對(duì)象概述
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