The TransferBytes property returns the number of bytes that
have been copied to or from the server. If this property
is read while a transfer is ongoing, the property returns the number
of bytes that have been copied up to that point. If read after a
transfer has completed, the total number of bytes copied is returned.
If the value would exceed 2,147,483,647 bytes (the maximum value
for a 32-bit integer) this property will return -1 to indicate an
overflow condition. If you are potentially transferring files larger
than 2 GiB in size, you should use the TransferBytesXL
property instead, which returns the number of bytes as a
Double floating-point value.
This property value is reset with every data transfer.