converting sql server rowversion to long or ulong?

Question

What is the proper type for the rowversion (timestamp) data type?

I know it is 8 bytes but i cannot find a link in MSDN which tell if it is a signed or unsigned long

Answer 1

Short answer: it doesn't matter but I'd choose UInt64.

Details: semantically it's equivalent to binary(8) so, strictly speaking, it's neither UInt64 nor Int64 but just a chunk of bytes (and in that way it should be managed). That said I'd choose UInt64 because it's an incrementing number to hold row version then (from a logic point of view) 0xFFFFFFFFFFFFFFFF should be greater than 0 and it's not true for Int64 (because 64 bits set to 1 give -1 and it's less than 0).

Edit: note that, for reasons known only in the innest SQL Server designers circle, ROWVERSION is big-endian (while - obviously - bigint is not) then you first need to reverse bytes, see this answer for a nice implementation.