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concurrency questionI'm using disconnected data I read data from an Access Data table to a data object I update the data object from a windows form I save the data from the data object to the Access Data table using a data adapter as follows: adpTeam.UpdateCommand = New OleDbCommand(sqlUpdate) adpTeam.UpdateCommand.Connection = aConnection adpTeam.UpdateCommand.ExecuteNonQuery() Since I'm not using datasets, how do I use optimistic concurrency and throw a concurrency exception if one occurs? If your sql update statement was written correctly using either the
verson number or saving-all-values approach then the adpTeam.UpdateCommand.ExecuteNonQuery() statement should raise a DBConcurrencyException when the number of rows affected by the update is zero which is generally a concurrency violation. In this way, you don't have to explicitly raise a concurrency exception. Andy William E Voorhees wrote: Show quoteHide quote > I'm updating an Access database in a windows multi-user environment. > > I'm using disconnected data > > I read data from an Access Data table to a data object > > I update the data object from a windows form > > I save the data from the data object to the Access Data table using a data > adapter as follows: > > > > adpTeam.UpdateCommand = New OleDbCommand(sqlUpdate) > > adpTeam.UpdateCommand.Connection = aConnection > > adpTeam.UpdateCommand.ExecuteNonQuery() > > > > Since I'm not using datasets, how do I use optimistic concurrency and throw > a concurrency exception if one occurs? I have a class containing public shared variables to hold the originally
read fields from the Team Table. (2 fields) I use the sql string listed below to update the description field. It does update the database when no concurrency problem occurs. If a concurrency does occur, the update does not occur because the Where Clause prevents it, but no exception is thrown. I have the update in a try / catch block but no exceptions are caught. I'm not sure why. It would seem that the numbers of rows affected by the update would be 0. Dim sqlUpdate As String = "Update TeamTable " & _ "Set TeamTable.Description = '" & strDescription & "' " & _ "Where TeamTable.ID = '" & cOrigTeam.strTeamID & "' And " & _ "TeamTable.Description = '" & cOrigTeam.strTeamDescription & "' " Show quoteHide quote "CaffieneRush" <CaffieneR***@gmail.com> wrote in message news:1153265464.608030.139960@i3g2000cwc.googlegroups.com... > If your sql update statement was written correctly using either the > verson number or saving-all-values approach then the > adpTeam.UpdateCommand.ExecuteNonQuery() > statement should raise a DBConcurrencyException when the number of rows > affected by the update is zero which is generally a concurrency > violation. > > In this way, you don't have to explicitly raise a concurrency > exception. > > Andy > > William E Voorhees wrote: >> I'm updating an Access database in a windows multi-user environment. >> >> I'm using disconnected data >> >> I read data from an Access Data table to a data object >> >> I update the data object from a windows form >> >> I save the data from the data object to the Access Data table using a >> data >> adapter as follows: >> >> >> >> adpTeam.UpdateCommand = New OleDbCommand(sqlUpdate) >> >> adpTeam.UpdateCommand.Connection = aConnection >> >> adpTeam.UpdateCommand.ExecuteNonQuery() >> >> >> >> Since I'm not using datasets, how do I use optimistic concurrency and >> throw >> a concurrency exception if one occurs? > It looks like you are using the saving-all-values approach to
optimistic concurrency. If you are rollong your own approach to db concurrency (rather than using dataadapter etc) then you'll probably need detect the conflict and throw your own exception as well. You can probably test the number of rows affect by the ExecuteNonQuery to detect the conflict. Something like: If adpTeam.UpdateCommand.ExecuteNonQuery() <= 0 Then Throw New DBConcurrencyException() 'Or handle the concurrency conflict here without throwing exception. End If HTH Andy William E Voorhees wrote: Show quoteHide quote > I have a class containing public shared variables to hold the originally > read fields from the Team Table. (2 fields) > > I use the sql string listed below to update the description field. It does > update the database when no concurrency problem occurs. If a concurrency > does occur, the update does not occur because the Where Clause prevents it, > but no exception is thrown. I have the update in a try / catch block but no > exceptions are caught. > > I'm not sure why. It would seem that the numbers of rows affected by the > update would be 0. > > Dim sqlUpdate As String = "Update TeamTable " & _ > > "Set TeamTable.Description = '" & strDescription & "' " & _ > > "Where TeamTable.ID = '" & cOrigTeam.strTeamID & "' And " & _ > > "TeamTable.Description = '" & cOrigTeam.strTeamDescription & "' " > > "CaffieneRush" <CaffieneR***@gmail.com> wrote in message > news:1153265464.608030.139960@i3g2000cwc.googlegroups.com... > > If your sql update statement was written correctly using either the > > verson number or saving-all-values approach then the > > adpTeam.UpdateCommand.ExecuteNonQuery() > > statement should raise a DBConcurrencyException when the number of rows > > affected by the update is zero which is generally a concurrency > > violation. > > > > In this way, you don't have to explicitly raise a concurrency > > exception. > > > > Andy > > > > William E Voorhees wrote: > >> I'm updating an Access database in a windows multi-user environment. > >> > >> I'm using disconnected data > >> > >> I read data from an Access Data table to a data object > >> > >> I update the data object from a windows form > >> > >> I save the data from the data object to the Access Data table using a > >> data > >> adapter as follows: > >> > >> > >> > >> adpTeam.UpdateCommand = New OleDbCommand(sqlUpdate) > >> > >> adpTeam.UpdateCommand.Connection = aConnection > >> > >> adpTeam.UpdateCommand.ExecuteNonQuery() > >> > >> > >> > >> Since I'm not using datasets, how do I use optimistic concurrency and > >> throw > >> a concurrency exception if one occurs? > > Thanks, I'll try throwing that exception myself.
Show quoteHide quote "CaffieneRush" <CaffieneR***@gmail.com> wrote in message news:1153334851.807964.210350@b28g2000cwb.googlegroups.com... > It looks like you are using the saving-all-values approach to > optimistic concurrency. > If you are rollong your own approach to db concurrency (rather than > using dataadapter etc) then you'll probably need detect the conflict > and throw your own exception as well. > > You can probably test the number of rows affect by the ExecuteNonQuery > to detect the conflict. Something like: > > If adpTeam.UpdateCommand.ExecuteNonQuery() <= 0 Then > Throw New DBConcurrencyException() > 'Or handle the concurrency conflict here without throwing exception. > End If > > HTH > Andy > > William E Voorhees wrote: >> I have a class containing public shared variables to hold the originally >> read fields from the Team Table. (2 fields) >> >> I use the sql string listed below to update the description field. It >> does >> update the database when no concurrency problem occurs. If a concurrency >> does occur, the update does not occur because the Where Clause prevents >> it, >> but no exception is thrown. I have the update in a try / catch block but >> no >> exceptions are caught. >> >> I'm not sure why. It would seem that the numbers of rows affected by the >> update would be 0. >> >> Dim sqlUpdate As String = "Update TeamTable " & _ >> >> "Set TeamTable.Description = '" & strDescription & "' " & _ >> >> "Where TeamTable.ID = '" & cOrigTeam.strTeamID & "' And " & _ >> >> "TeamTable.Description = '" & cOrigTeam.strTeamDescription & "' " >> >> "CaffieneRush" <CaffieneR***@gmail.com> wrote in message >> news:1153265464.608030.139960@i3g2000cwc.googlegroups.com... >> > If your sql update statement was written correctly using either the >> > verson number or saving-all-values approach then the >> > adpTeam.UpdateCommand.ExecuteNonQuery() >> > statement should raise a DBConcurrencyException when the number of rows >> > affected by the update is zero which is generally a concurrency >> > violation. >> > >> > In this way, you don't have to explicitly raise a concurrency >> > exception. >> > >> > Andy >> > >> > William E Voorhees wrote: >> >> I'm updating an Access database in a windows multi-user environment. >> >> >> >> I'm using disconnected data >> >> >> >> I read data from an Access Data table to a data object >> >> >> >> I update the data object from a windows form >> >> >> >> I save the data from the data object to the Access Data table using a >> >> data >> >> adapter as follows: >> >> >> >> >> >> >> >> adpTeam.UpdateCommand = New OleDbCommand(sqlUpdate) >> >> >> >> adpTeam.UpdateCommand.Connection = aConnection >> >> >> >> adpTeam.UpdateCommand.ExecuteNonQuery() >> >> >> >> >> >> >> >> Since I'm not using datasets, how do I use optimistic concurrency and >> >> throw >> >> a concurrency exception if one occurs? >> > > William,
Optimistic concurrency is based on testing an original value to a existing value in the database. If there is a difference in that, than you have a concurrency error. (There is something changed meanwhile) You can take a timestamp, or all the data that is used as the dataadapter in versions 2002/2003 does it and standard in the 2005 version. If you want to do that, than you should in one or the other way save somewhere an/the original value of your rows. I hope this helps, Cor Show quoteHide quote "William E Voorhees" <w**@cinci.rr.com> schreef in bericht news:QBdvg.38360$u11.27191@tornado.ohiordc.rr.com... > I'm updating an Access database in a windows multi-user environment. > > I'm using disconnected data > > I read data from an Access Data table to a data object > > I update the data object from a windows form > > I save the data from the data object to the Access Data table using a data > adapter as follows: > > > > adpTeam.UpdateCommand = New OleDbCommand(sqlUpdate) > > adpTeam.UpdateCommand.Connection = aConnection > > adpTeam.UpdateCommand.ExecuteNonQuery() > > > > Since I'm not using datasets, how do I use optimistic concurrency and > throw a concurrency exception if one occurs? > > If I would use a timestamp, do I add the timestamp field to each table in
the Access database and manually update the timestamp at every update, or does an mdb database file have a way to update a timestamp field each time a row is changed? Show quoteHide quote "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> wrote in message news:OAeWwAvqGHA.4684@TK2MSFTNGP05.phx.gbl... > William, > > Optimistic concurrency is based on testing an original value to a existing > value in the database. > > If there is a difference in that, than you have a concurrency error. > (There is something changed meanwhile) > > You can take a timestamp, or all the data that is used as the dataadapter > in versions 2002/2003 does it and standard in the 2005 version. > > If you want to do that, than you should in one or the other way save > somewhere an/the original value of your rows. > > I hope this helps, > > Cor > > > "William E Voorhees" <w**@cinci.rr.com> schreef in bericht > news:QBdvg.38360$u11.27191@tornado.ohiordc.rr.com... >> I'm updating an Access database in a windows multi-user environment. >> >> I'm using disconnected data >> >> I read data from an Access Data table to a data object >> >> I update the data object from a windows form >> >> I save the data from the data object to the Access Data table using a >> data adapter as follows: >> >> >> >> adpTeam.UpdateCommand = New OleDbCommand(sqlUpdate) >> >> adpTeam.UpdateCommand.Connection = aConnection >> >> adpTeam.UpdateCommand.ExecuteNonQuery() >> >> >> >> Since I'm not using datasets, how do I use optimistic concurrency and >> throw a concurrency exception if one occurs? >> >> > > William,
I am not sure about Jet (access), but the purpose of a timestamp is that it is automaticly updated to the latest changetime. Why don't you just try it? Cor Show quoteHide quote "William E Voorhees" <w**@cinci.rr.com> schreef in bericht news:82Cvg.55639$Eh1.47156@tornado.ohiordc.rr.com... > If I would use a timestamp, do I add the timestamp field to each table in > the Access database and manually update the timestamp at every update, or > does an mdb database file have a way to update a timestamp field each time > a row is changed? > > "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> wrote in message > news:OAeWwAvqGHA.4684@TK2MSFTNGP05.phx.gbl... >> William, >> >> Optimistic concurrency is based on testing an original value to a >> existing value in the database. >> >> If there is a difference in that, than you have a concurrency error. >> (There is something changed meanwhile) >> >> You can take a timestamp, or all the data that is used as the dataadapter >> in versions 2002/2003 does it and standard in the 2005 version. >> >> If you want to do that, than you should in one or the other way save >> somewhere an/the original value of your rows. >> >> I hope this helps, >> >> Cor >> >> >> "William E Voorhees" <w**@cinci.rr.com> schreef in bericht >> news:QBdvg.38360$u11.27191@tornado.ohiordc.rr.com... >>> I'm updating an Access database in a windows multi-user environment. >>> >>> I'm using disconnected data >>> >>> I read data from an Access Data table to a data object >>> >>> I update the data object from a windows form >>> >>> I save the data from the data object to the Access Data table using a >>> data adapter as follows: >>> >>> >>> >>> adpTeam.UpdateCommand = New OleDbCommand(sqlUpdate) >>> >>> adpTeam.UpdateCommand.Connection = aConnection >>> >>> adpTeam.UpdateCommand.ExecuteNonQuery() >>> >>> >>> >>> Since I'm not using datasets, how do I use optimistic concurrency and >>> throw a concurrency exception if one occurs? >>> >>> >> >> > > 
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