Datetime and the missing milliseconds

another datetime problem...

When I send a .net Datetime as a param to a SQL Server sproc, the milliseconds disappear.

I am returning a lastUpdatedDate field from a table in SQL Server to my asp.net page along with updateable table data. The user makes their updates and then submits the form which sends the data to a sproc which makes the update. The procedure makes a check that the lastUpdatedDate submitted back from the form is still the same as the one in the database (to guard against lost updates)

However, when the lastUpdatedDate gets back into SQL server it is missing the milliseconds component - they have been set to 000. I've been tearing my hair out trying to find the point at which the milliseconds disappear and why - but to no avail.

The way I'm doing it is storing the lastUpdatedDate in a .net datetime, passing this into viewstate and then when the user submits the update, retrieving it from ViewState back into the datetime variable and then submitting it to the sproc using a parameter of SqlDbType.Datetime

I have put bits of debug code at every point in the .net processing to look at the datetime and the milliseconds are always there... its only when the value gets picked up in SQL Server that they have disappeared

Any ideas?

MaracatuIs the data type in the data base table DateTime or SmallDateTime? If it's SmallDateTime that might be causing the truncation of the milliseconds (and seconds).|||Its datetime.
The milliseconds go missing when the datetime is retrieved from ViewState after a round trip to the client (bizarrely if the datetime is placed in Viewstate and immediately retrieved and sent to the database no problem occurs).

I have now solved the problem by storing a String value of the datetime, including the milliseconds in ViewState rather than puting the datetime value in there directly.|||Interesting, I now recall having a similar problem with disappearing milliseconds. It wasn't a concern and so I didn't check up on it but I bet that was the reason.

Probably when a datetime is placed into ViewState it serializes it as a string but without milliseconds. But it doesn't actually get serialized until just before the page it sent back to the client so if you stick it into ViewState and pull it back out it's still the original datetime.