使用BinaryWriter时，为什么二进制文件的大小不会减少

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

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 []：

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 []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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