As I said, reading is a one-way operation. Whatever your current index, you will always read from the stream one byte at a time, and in doing so, move your cursor forward by one in the index. So, your next Read operation always starts one byte after wherever you last read. The trick here is that every time you want to read anything more than a single byte (which you can simply assign to a variable of the byte type), you have to read it into a destination array. So, you'll need to declare and assign a target destination array before you can read it. Let's see this in action; first, though, remove the Seek operation so that every time you run your app, you don't grow your text file:
using (Stream ioStream = new FileStream(@"../stream_demo_file.txt", ...
