c# binarywriter write string

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Howdy, I intend to write char to a binary file with binarywriter in C#:

FileStream filestream = new FileStream("test.t", FileMode.Create, FileAccess.Write, FileShare.Read, 1024);
      BinaryWriter binaryWriter = new BinaryWriter(filestream);
      binaryWriter.Write("hello");
      binaryWriter.Write("AAA");
      binaryWriter.Close();
      file.Close();

But when I exam the output file I found there are extra bytes in the front of each string, such that the hello become six chars: 0x05 'h''e''l''l''o' and "AAA" become four chars: 0x03'A''A''A'

Anyone know why?

VS 2008
Test in win7 and xp.

Posted 1-May-11 1:00am

Du Sijun

Updated 1-May-11 7:14am

v3

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3 solutions

Solution 3

If you don't want or need the length byte you can call Write with a Char [] array instead of a String.

Posted 6-Sep-12 9:41am

S. Moenssen

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OriginalGriff · Accepted Answer · 2011-05-01T02:20:00

Solution 1

Yes.

Simple: the prefix is the lengths. If you try with the code you actually wrote here, (and fix the compilation error - it should be "filestream.Close()" - you will find that the file contains

0x05  - number of characters in the string "hello"
'h'
'e'
'l'
'l'
'o'
0x03  - number of characters in the string "AAA"
'A'
'A'
'A'

The version of this in your application had a string of ten characters to start with, rather than five

Posted 1-May-11 2:20am

OriginalGriff

Comments

Du Sijun 1-May-11 13:18pm

Yes, it ought to be 0x05

Sergey Alexandrovich Kryukov 1-May-11 18:17pm

You know how string works, nice of you to tell to those how don't... :-) My 5.
--SA

Richard MacCutchan · Accepted Answer · 2011-05-01T02:26:00

Solution 2

Strings are preceded by a length byte as described here[^]. It's always best to read the documentation first.

Posted 1-May-11 2:26am

Richard MacCutchan

Comments

Sergey Alexandrovich Kryukov 1-May-11 18:17pm

You know that, too... :-) My 5.
--SA