What Does "commit" Mean

Question

I have a DataGrid with a DataTable as the ItemsSource. Leaving out columns irrelevant to this post the DataTable is:

MyTable Columns.Add("TransactionID", GetType(Integer))
MyTable Columns.Add("Amount", GetType(Decimal))

and the DataGrid (again, leaving other columns) is:

<DataGrid>
	<DataGrid.Columns>
		<DataGridTextColumn Binding="{Binding TransactionID}"
	Amount, StringFormat=C2}"
	</DataGrid.Columns>
</DataGrid>

I keep a running sum of the "Amount" values as rows are added to the table as follows:

Private Sub MyGrid_RowEditEnding(sender As Object, e As DataGridRowEditEndingEventArgs) Handles MyGrid.RowEditEnding
    RunningSum = CDec(MyTable.Compute("SUM(Amount)", ""))
End Sub

However this does not work because even though the row being added is "committed", it apparently is not actually in the table. That is, the running sum does not include the "Amount" in the row just added. What is the right way to do this?

Answer 1

Hi @RogerSchlueter-7899,

It seems like the issue you're facing is related to the timing of when the RowEditEnding event is triggered in relation to when the row is actually added to the DataTable. The RowEditEnding event might be fired before the changes are fully committed to the DataTable.

To ensure that you include the newly added row in your running sum calculation, you can try using the RowEditEnding event to update the running sum after the changes have been committed. You can achieve this by handling the RowEditEnding event and then updating the running sum within the Dispatcher to postpone it until after the current event has been processed.

Private Sub MyGrid_RowEditEnding(sender As Object, e As DataGridRowEditEndingEventArgs) Handles MyGrid.RowEditEnding

    Dispatcher.BeginInvoke(Sub()
                               RunningSum = CDec(MyTable.Compute("SUM(Amount)", ""))
                           End Sub, DispatcherPriority.ContextIdle)
End Sub

Best Regards.

Jiachen Li

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