Stream.Write Method

When overridden in a derived class, writes a sequence of bytes to the 
current stream and advances the current position within this stream by 
the number of bytes written. 

const int size = 4096;
byte[] bytes = new byte[4096];
int numBytes;
while((numBytes = input.Read(bytes, 0, size)) > 0)
    output.Write(bytes, 0, numBytes);