Cast rowversion to bigint

Question

In my C# program I don't want to work with byte array, therefore I cast rowversion data type to bigint:

SELECT CAST([version] AS BIGINT) FROM [dbo].[mytable]

So I receive a number instead of byte array. Is this conversion always successful and are there any possible problems with it? If so, in which data type should I cast rowversion instead?

Answer 1

rowversion and bigint both take 8 bytes so casting seems possible. However, the difference is that bigint is a signed integer, while rowversion is not.

This is a max value of rowversion that will cast properly to max positive bigint number (9223372036854775807):

select cast(0x7FFFFFFFFFFFFFFF as bigint)

But starting from here, you'll be getting negative numbers:

select cast(0x8000000000000000 as bigint)

I didn't check if the latter cast throws an error in C#.

You problably won't reach more than 9223372036854775807 rows in your table, but still it's something you should know about, and I personally wouldn't recommend doing this unless you are certain that this problem will never occur in your solution.