使用BinaryWriter时，为什么二进制文件的大小不会减少 [英] Why Does The Size Of Binary File Does Not Decrease While Using BinaryWriter

问题描述

为什么从第二种方法中删除Int时文件大小不会减少到4byte。

Why The File Size Does Not Decreases To 4byte While Removing Int From 2nd Method.

 static void write()
        {
            BinaryWriter sr = new BinaryWriter(File.OpenWrite("bin.txt"));
            int m;
            m = 123456;
            sr.Write(m);
            m = 122;
            sr.Write(m);
            sr.Close();
        }
While Using Above Function The Size Of bin.txt Is 8 Byte .

But While Removing m = 122 From The Below Function And Running The Same program Again  , The File Size Has To Be Changed 4Byte , But It Is Not Changing 4 Byte .It Is Being Same As 8 Byte   
static void write()
        {
            BinaryWriter sr = new BinaryWriter(File.OpenWrite("bin.txt"));
            int m;
            m = 123456;
            sr.Write(m);
            sr.Close();
        }
While Running Below Function By Adding double Type In It Than The Size Of File Of Size Increases From 8 To 12 . 

 static void write()
        {
            BinaryWriter sr = new BinaryWriter(File.OpenWrite("bin.txt"));
            int m;
            m = 123456;
            sr.Write(m);
            double pp = 1233.00;
            sr.Write(pp);
            sr.Close();
        }

为什么从第二种方法中删除Int时文件大小不会减少到4byte

Why The File Size Does Not Decreases To 4byte While Removing Int From 2nd Method

推荐答案

这是因为您正在写入一个比您正在编写的数据更大的现有文件。来自 OpenWrite [ ^ 描述：

That happens because you are writing to an already existing file that has a larger size than the data you are writing. From the OpenWrite[^] description:

Quote：

如果你覆盖一个更长的字符串（例如这是一个使用较短的字符串（例如Second run）测试OpenWrite方法，该文件将包含混合字符串（OpenWrite方法的第二次运行测试）。

If you overwrite a longer string (such as "This is a test of the OpenWrite method") with a shorter string (such as "Second run"), the file will contain a mix of the strings ("Second runtest of the OpenWrite method").

如果您之前创建新文件或删除它，则大小为4.



[更新]

如果您想要现有要截断的文件，使用适当模式的 File.Open（）或只是 File.Create（） [ ^ ]：

If you create a new file or delete it before, the size will be 4.

[UPDATE]
If you want existing files to be truncated, use File.Open() with the appropiate mode or just File.Create()[^]:

BinaryWriter sr = new BinaryWriter(File.Create("bin.txt"));

File.OpenWrite（）使用 FileMode.OpenOrCreate 而 File.Create（）使用 FileMode.Create 。请参阅 FileMode [ ^ ]了解模式的描述。

File.OpenWrite() uses FileMode.OpenOrCreate while File.Create() uses FileMode.Create. See FileMode[^] for a description of the modes.

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