[c#] Writing String to Stream and reading it back does not work

I want to write a String to a Stream (a MemoryStream in this case) and read the bytes one by one.

stringAsStream = new MemoryStream();
UnicodeEncoding uniEncoding = new UnicodeEncoding();
String message = "Message";

stringAsStream.Write(uniEncoding.GetBytes(message), 0, message.Length);

Console.WriteLine("This:\t\t" + (char)uniEncoding.GetBytes(message)[0]);
Console.WriteLine("Differs from:\t" + (char)stringAsStream.ReadByte());

The (undesired) result I get is:

This:         M
Differs from: ?

It looks like it's not being read correctly, as the first char of "Message" is 'M', which works when getting the bytes from the UnicodeEncoding instance but not when reading them back from the stream.

What am I doing wrong?

The bigger picture: I have an algorithm which will work on the bytes of a Stream, I'd like to be as general as possible and work with any Stream. I'd like to convert an ASCII-String into a MemoryStream, or maybe use another method to be able to work on the String as a Stream. The algorithm in question will work on the bytes of the Stream.

You're using message.Length which returns the number of characters in the string, but you should be using the nubmer of bytes to read. You should use something like:

byte[] messageBytes = uniEncoding.GetBytes(message);
stringAsStream.Write(messageBytes, 0, messageBytes.Length);

You're then reading a single byte and expecting to get a character from it just by casting to char. UnicodeEncoding will use two bytes per character.

As Justin says you're also not seeking back to the beginning of the stream.

Basically I'm afraid pretty much everything is wrong here. Please give us the bigger picture and we can help you work out what you should really be doing. Using a StreamWriter to write and then a StreamReader to read is quite possibly what you want, but we can't really tell from just the brief bit of code you've shown.

Try this "one-liner" from Delta's Blog, String To MemoryStream (C#).

MemoryStream stringInMemoryStream =
   new MemoryStream(ASCIIEncoding.Default.GetBytes("Your string here"));

The string will be loaded into the MemoryStream, and you can read from it. See Encoding.GetBytes(...), which has also been implemented for a few other encodings.

I think it would be a lot more productive to use a TextWriter, in this case a StreamWriter to write to the MemoryStream. After that, as other have said, you need to "rewind" the MemoryStream using something like stringAsStream.Position = 0L;.

stringAsStream = new MemoryStream();

// create stream writer with UTF-16 (Unicode) encoding to write to the memory stream
using(StreamWriter sWriter = new StreamWriter(stringAsStream, UnicodeEncoding.Unicode))
{
  sWriter.Write("Lorem ipsum.");
}
stringAsStream.Position = 0L; // rewind

Note that:

StreamWriter defaults to using an instance of UTF8Encoding unless specified otherwise. This instance of UTF8Encoding is constructed without a byte order mark (BOM)

Also, you don't have to create a new UnicodeEncoding() usually, since there's already one as a static member of the class for you to use in convenient utf-8, utf-16, and utf-32 flavors.

And then, finally (as others have said) you're trying to convert the bytes directly to chars, which they are not. If I had a memory stream and knew it was a string, I'd use a TextReader to get the string back from the bytes. It seems "dangerous" to me to mess around with the raw bytes.

You need to reset the stream to the beginning:

stringAsStream.Seek(0, SeekOrigin.Begin);
Console.WriteLine("Differs from:\t" + (char)stringAsStream.ReadByte());

This can also be done by setting the Position property to 0:

stringAsStream.Position = 0