c# binarywriter write string

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.

Tags: C#, String