OK, well, that solution wasn't quite as solid as I thought yesterday. I was
just hiding the problem. After more research apparently this is a known bug
since 2002 although I can find no reference to it when searching the MS KB.
There is a nice little writeup on it with workarounds at
www.falafel.com/flogs
I chose to drop the expression columns, do the update, and restore them.
Simply setting the expression to empty or Nothing raised an "instance of
object not set" exception. Still needs more testing but it appears to get
around the problem. Since I have a separate data access layer I do it at
that level avoiding the problems (I think!) with dropping the columns and
databinding.
Carl
Here is a simple code snippet:
' save expression columns and delete them out so updates will go
through
Dim dcLastNameFirstExp As DataColumn =
inDS.Customer.Columns("LastNameFirst")
Dim dcCityStateZipExp As DataColumn =
inDS.Customer.Columns("CityStateZip")
inDS.Customer.Columns.Remove("LastNameFirst")
inDS.Customer.Columns.Remove("CityStateZip")
' save customer changes and additions
Me.sdaCustomer.Update(inDS.Customer.Select("", "", _
DataViewRowState.Added Or DataViewRowState.ModifiedCurrent))
' save all phone number changes, including deletes
Me.sdaPhoneNumber.Update(inDS.CustomerPhoneNumber)
' process customer deletes
Me.sdaCustomer.Update(inDS.Customer)
"clorentson" wrote:
[color=blue]
> I was running into the same problem and, based on wht I learned here, decided
> to catch and ignore the exception.
>
> Alternative to manually accepting changes at the table level would be to
> accept all changes in the dataset at the end of the updates.
>
> Carl
>
> Here is the code snippet:
>
>
> Try
> Me.sdaOrders.Update(inDS.Orders.Select("", "", _
> DataViewRowState.Added Or
> DataViewRowState.ModifiedCurrent))
> Catch RO_exception As Data.ReadOnlyException
> ' do nothing, need to catch it for the expression column
> ' DO NOT Accept changes here, more changes to be saved later!
> End Try
> ' can add, change, and delete because no subordinate tables
> Me.sdaOrderPayments.Update(inDS.OrderPayments)
>
> ' only add or modify, can't delete because there are subordinate
> tables
> Me.sdaOrderDetails.Update(inDS.OrderDetails.Select ("", "", _
> DataViewRowState.Added Or DataViewRowState.ModifiedCurrent))
> ' can add, change, and delete because no subordinate tables
> Me.sdaOrderMiscCharges.Update(inDS.OrderDetailMisc Charges)
> ' only add or modify, can't delete because there are subordinate
> tables
>
> Me.sdaOrderDetailComponents.Update(inDS.OrderDetai lComponents.Select("", "", _
> DataViewRowState.Added Or DataViewRowState.ModifiedCurrent))
> ' can add, change, and delete because no subordinate tables
>
> Me.sdaOrderDetailComponentSpeficiations.Update(inD S.OrderDetailComponentSpecifications)
>
> ' now pick up the deletes, from the bottom up
> Me.sdaOrderDetailComponents.Update(inDS.OrderDetai lComponents)
> Me.sdaOrderDetails.Update(inDS.OrderDetails)
> Try
> Me.sdaOrders.Update(inDS.Orders)
> Catch RO_exception As Data.ReadOnlyException
> ' accept changes manually and continue
> inDS.Orders.AcceptChanges()
> End Try
>
> "Aaron Smith" wrote:
>[color=green]
> > I fixed this problem. The solution is quite simple. Whenever you call
> > Update on the dataadapter, just remove the expression and then add it
> > back after the update is finished:
> >
> > Dim dc As DataColumn = DataSet.Table.Columns.Item("ExpCol")
> > Dim exp As String = dc.Expression
> > dc.Expression = ""
> > Try
> > DataAdapter.Update(DataSet, "Table")
> > Catch ex As Exception
> > System.Windows.Forms.MessageBox.Show(ex.Message(), "Error")
> > Finally
> > dc.Expression = exp
> > End Try
> >
> > I tried to just remove the whole column, then add it back in, but for
> > some reason I was getting an error message that the column wasn't a
> > datacolumn or datarelation, so I simplified...
> >
> > Aaron Smith wrote:[color=darkred]
> > > I'm still getting this error, does anyone have any more ideas? I removed
> > > the field from the schema and manually add it and I still get the error
> > > message. The record actually saves, but this error just pops up.. If
> > > there a way to turn error checking off for certain fields? Is it just a
> > > property I am not setting?
> > >
> > > Aaron Smith wrote:
> > >
> > >> I just added it to the Dataset Schema and then set the expression in
> > >> the new procedure of the form...
> > >>
> > >> CoursesDS1.InstClasses.FullNameColumn.Expression =
> > >> "Parent(InstructorsInstClasses).First_Name + ' ' +
> > >> Parent(InstructorsInstClasses).Last_Name"
> > >>
> > >> Thats the expression...
> > >>
> > >> If that is the only line of code in there, and I don't manually set
> > >> the value, it still does not work.. I still get the same message.
> > >> Should I remove that column from the schema and manually create the
> > >> column and add it to the table?? I think I will try that while waiting
> > >> for other suggestions.
> > >>
> > >> Aaron
> > >>
> > >> Chris, Master of All Things Insignificant wrote:
> > >>
> > >>> How did you add the column to the dataset? You added it to the
> > >>> Table? Can you post some simplified code that shows the problem?
> > >>>
> > >>> Chris
> > >>>
> > >>> "Aaron Smith" <thespirit-1-@smithcentral.net> wrote in message
> > >>> news:bbnwd.947$1o1.14@newssvr19.news.prodigy.com.. .
> > >>>
> > >>>> Ok. I have a dataset that has multiple tables in it. In one of the
> > >>>> child tables, I have a column that I added to the DataSet (Not in
> > >>>> the DataSource). This column does not need to be stored in the data
> > >>>> on the datasource. It simply gets the first name and last name of an
> > >>>> instructor and displays it in the grid. I have two major
> > >>>> problems.... One, it doesn't display in the column until the row is
> > >>>> saved, (Even after calling a refresh on the grid) and two, I am
> > >>>> getting a Cannot change ReadOnly property of the expression column
> > >>>> error message when I try to update the datasource. I found a lot of
> > >>>> confusing information that dealt with the column updating the
> > >>>> datasource, etc etc. The column is in none of the commands attached
> > >>>> to the data adapters.
> > >>>>
> > >>>> For the column refresh problem, I added code to manually fill in
> > >>>> that field when leaving a previous column and that seemed to work,
> > >>>> however, it doesn't always show when doing a refresh. I have to
> > >>>> navigate back to that column in order to see it.
> > >>>>
> > >>>> Any ideas on either problem?
> > >>>> Aaron
> > >>>> --
> > >>>> ---
> > >>>> Aaron Smith
> > >>>> Remove -1- to E-Mail me. Spam Sucks.
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>
> > >>
> > >
> > >[/color]
> >
> >
> > --
> > ---
> > Aaron Smith
> > Remove -1- to E-Mail me. Spam Sucks.
> >[/color][/color]
