I searched Usenet and found some posts with people having similar
problems, I'm wondering if any MVPs or anyone else knows if this is a
confirmed bug and if MS plans to do anything about it.  First let me
quite the MSDN documentation:

public virtual void Write (  string value  )

A length-prefixed string represents the string length by prefixing to
the string a single byte or word that contains the length of that
string. This method writes a length-prefixed string to this stream
using the BinaryWriter instance's current Encoding. -----This method
first writes the length of the string as a four-byte unsigned
integer-----, and then writes that many characters to the stream.

the section enclosed in ----- ----- indicates where the "bug" arises.
There's either a bug in the documentation or the function, one or the
other.

The following sample program should demonstrate:

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace WriterTest
{
  class Program
  {
     static void Main(string[] args)
     {
        using (MemoryStream MStream = new MemoryStream())
        {
           BinaryWriter Writer = new BinaryWriter(MStream);

           string TestString = "This is a test string";
           System.Console.WriteLine("The writer is at position {0}.",
Writer.BaseStream.Position);

           Writer.Write(TestString);

           System.Console.WriteLine("Position after
BinaryWriter.Write(String) - {0},  String length - {1},  # of bytes
for size - {2}.", Writer.BaseStream.Position, TestString.Length,
Writer.BaseStream.Position - (long)TestString.Length);
           System.Console.ReadLine();
        }
     }
  }
}

Here's the output.

The writer is at position 0.
Position after BinaryWriter.Write(String) - 22,  String length - 21,
# of bytes for size - 1.