How to read system time in WPF for updating SQL Server timestamp field?

For the purpose of organizing streamlined database timer-based polling, with every updating of database table I need to update a timestamp field in a SQL Server 2008 database (the开发者_运维问答n poll, read its value, compare with the value in front-end and making decisions about reading the whole table).

Regarding all this, how I could read system time for writing timestamp? What data format of SQL Server field to use (DataTime or Time)? And how values of this format could be compared?

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Are you talking about a database column of TIMESTAMP type??

Those are binary timestamp that SQL Server will update internally - they have nothing to do with date and/or time - it's just a binary-encoded counter, really. These fields are handled by the system, and they're reliable and very accurate - if you want to have some kind of an optimistic concurrency locking mechanism, use this field type.

If you want a DATETIME field containing a date and time of the last modification, you're best option would be to have a AFTER INSERT/AFTER UPDATE trigger on that table which sets the last updated column to the current date/time of the SQL Server automatically, without you having to do anything about it.

DATETIME in SQL Server 2005 is accurate to about 3.33ms - in SQL Server 2008, DATETIME2 can be made accurate to 100ns, if needed. As such, do not rely on a DATETIME column for 100% accurate checking whether something has changed or not! The 3.33ms accuracy might give misleading results!