sql TimeStamp column

[fundez]

Hello,

I'm using a sql timestamp field to control concurrency. I don't think I'm handling correctly on the c# side. Could someone take a peak at code below and verify it's correct. Thank You!

I'm using this to load it via a DataReader

LoadProperty(LastChangedProperty, dr.GetValue("LastChanged") as Byte[]);

and this to pass it back to sql.

cmd.Parameters.AddWithValue("@LastChanged", ReadProperty(LastChangedProperty)).DbType = DbType.Binary;
cmd.Parameters.AddWithValue("@LastChanged", SqlDbType.Timestamp).Direction = ParameterDirection.InputOutput;

and finally this to read the return value on an update.
LoadProperty(LastChangedProperty, cmd.Parameters["@LastChanged"].Value as Byte[]);

The property declaration is below just in case.
public static readonly PropertyInfo<Byte[]> LastChangedProperty = RegisterProperty<Byte[]>(p => p.LastChanged, "Last Changed");
[Display(Name = "Last Changed")]
public Byte[] LastChanged
{
get { return GetProperty(LastChangedProperty); }
set { SetProperty(LastChangedProperty,value); }
}

[ajohnstone-ks]

You're handling it correctly in that you treat it as a byte array. But its not a value you'd ever show to the user. What you normally do is when you fetch an existing record you put it in your BO, then in your data portal update you do the normal update SQL, but you add WHERE TimeStamp = @timestamp. If the records current Timestamp value is different than yours, you (purposefully) don't update the record, because someone else already has and you let the user know they have stale data. If your update is successful though, you read the records new value and put that back into your BO. The SQL timestamp is for collision detection, not a last changed date.

sorry if that is already your understanding of things, I just thought it odd to have it displayed to the user and labled "Last Changed"

[fundez]

No worries, clarification is always helpful. User is never seeing this. I'm thinking it's wrong because I'm hitting issue where timestamp doesn't match when I'm updating.

[ajohnstone-ks]

No worries, clarification is always helpful. User is never seeing this. I'm thinking it's wrong because I'm hitting issue where timestamp doesn't match when I'm updating.

Hmm, well if the value you load from the db to your BO doesn't match when you update, it would have to be because another process updated the row since you get the data into your BO. Or if something is changing the value in your BO I suppose. But the code you posted looks fine to me.

AFAIK, you can't set values into a timestamp column and SQL will take care of increasing the value anytime there's an UPDATE done on the row.

I don't think it matters, but timestamp has been deprecated, rowversion is the replacement, but you still treat it the same and its a byte array.