Need help understanding Stream.Read()

Question

I am a little confused as to the steps of reading a file into buffer gradually.

from the MSDN docs

public abstract int Read(
    byte[] buffer,
             


        

Answer 1

Read will read whatever's available (blocking until something is available) but there may not be enough data ready to fill the buffer to start with.

Imagine downloading data over the network - there may be megabytes of data to download, but only some of it is available to start with. So you need to keep calling Read() until you've read as much as you want.

Stream.Read will read at most the number of bytes you've asked for, but can easily read less. Admittedly for local file streams I suspect it always reads as much as you've asked for unless the file is shorter, but that's not true of streams in general, and I don't believe it's guaranteed even for local file streams.