c#
int totalBytesRead = 0;
while (true)
{
    int bytesRead = await source.ReadAsync(buffer.AsMemory(totalBytesRead, DefaultCopyBufferSize - totalBytesRead));
    if (bytesRead == 0)
        break;

    totalBytesRead += bytesRead;
    if (totalBytesRead >= DefaultCopyBufferSize || bytesRead == 0)
    {
        await destination.WriteAsync(buffer.AsMemory(0, totalBytesRead));
        progress.Increment(totalBytesRead);
        totalBytesRead = 0;
    }
}

c#
int totalBytesRead = 0;
while (true)
{
    int bytesRead = await source.ReadAsync(buffer.AsMemory(totalBytesRead, DefaultCopyBufferSize - totalBytesRead));
    if (bytesRead == 0)
        break;

    totalBytesRead += bytesRead;
    if (totalBytesRead >= DefaultCopyBufferSize || bytesRead == 0)
    {
        await destination.WriteAsync(buffer.AsMemory(0, totalBytesRead));
        progress.Increment(totalBytesRead);
        totalBytesRead = 0;
    }
}

while ((bytesRead = await source.ReadAsync(memory)) > 0)

while ((bytesRead = await source.ReadAsync(memory)) > 0)