Is an UDP Datagram always guaranteed to arrive in one piece?

[bukkideme]

Hi Folks!

I am trying to understand UDP better. I know there is a max Datagram size, 65,507 byte for ipv4.
The question is that, if I send one data package below this size, is it always guaranteed to arrive at the receiver as one piece?
For example, i send exactly 10,000 bytes (below the datagram size limit). Is it always going to be this exact 10,000 bytes arriving at the receiver side? I know that UDP is not guaranteeing that a package cannot get lost, neither the proper sending order of different datagrams. This is not an issue for me. But I would like to know, if I can always expect the same datagram if it arrives.
I understand that at lower levels, there might be fragmentations, driver level things, driver assembling the parts, basic checksum check, etc. I do not care. What I care about, at the OS/C# level, whether I can expect always the same datagram or not?

The motivation: I wonder if I could neglect data frame leading marker/ending marker of the messages. If I know that I always get the exact same 10,000 bytes, I can be sure that the data is at the proper positions in it. No need to re-assembling like in the case of a RS232 datastream between an embedded PIC and PC for example...

Thanks! :)