Why Does The Size Of Binary File Does Not Decrease While Using BinaryWriter

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

C#

 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();
        }

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

Posted 17-Dec-15 22:20pm

Hitesh Jain

Updated 17-Dec-15 22:25pm

Andy Lanng

v2

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Comments

BillWoodruff 18-Dec-15 4:35am

Consider that there may be a minimum allocated size for the binary stream ?

BillWoodruff 18-Dec-15 4:37am

This is in effect a repost: you should add this content to your first question posted only a few hours ago, then delete this post.

Jochen Arndt 18-Dec-15 4:45am

Too late. I have just answered it without recognizing that it is a repost.

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Jochen Arndt · Answer 1 · 2015-12-17T22:43:00

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:
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”).

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()[^]:

C#

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

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