Upload a file to an FTP server from a string or stream

Just copy your stream to the FTP request stream:

Stream requestStream = ftpRequest.GetRequestStream();
stream.CopyTo(requestStream);
requestStream.Close();

---

For a string (assuming the contents is a text):

byte[] bytes = Encoding.UTF8.GetBytes(data);

using (Stream requestStream = request.GetRequestStream())
{
    requestStream.Write(bytes, 0, bytes.Length);
}

Or even better use the StreamWriter:

using (Stream requestStream = request.GetRequestStream())
using (StreamWriter writer = new StreamWriter(requestStream, Encoding.UTF8))
{
    writer.Write(data);
}

If the contents is a text, you should use the text mode:

request.UseBinary = false;