Eric's BizTalk 2004/2006/2009 blog

/// <summary>
/// Reads data from a stream until the end is reached. The
/// data is returned as a byte array. An IOException is
/// thrown if any of the underlying IO calls fail.
/// </summary>
/// <param name="stream">The stream to read data from</param>
/// <param name="initialLength">The initial buffer length</param>
public static byte[] ReadFully (Stream stream, int initialLength)
{
    // If we've been passed an unhelpful initial length, just
    // use 32K.
    if (initialLength < 1)
    {
        initialLength = 32768;
    }
    
    byte[] buffer = new byte[initialLength];
    int read=0;
    
    int chunk;
    while ( (chunk = stream.Read(buffer, read, buffer.Length-read)) > 0)
    {
        read += chunk;
        
        // If we've reached the end of our buffer, check to see if there's
        // any more information
        if (read == buffer.Length)
        {
            int nextByte = stream.ReadByte();
            
            // End of stream? If so, we're done
            if (nextByte==-1)
            {
                return buffer;
            }
            
            // Nope. Resize the buffer, put in the byte we've just
            // read, and continue
            byte[] newBuffer = new byte[buffer.Length*2];
            Array.Copy(buffer, newBuffer, buffer.Length);
            newBuffer[read]=(byte)nextByte;
            buffer = newBuffer;
            read++;
        }
    }
    // Buffer is now too big. Shrink it.
    byte[] ret = new byte[read];
    Array.Copy(buffer, ret, read);
    return ret;
}