No more data displayed when using SumFunction on GridViewExpressionColumn

[HDC]

I have defined following grid:

<telerik:RadGridView x:Name="invoiceDetailGrid"
                                   ItemsSource="{Binding ElementName=invoiceDetailDomainDataSource, Path=DataView}"
                                   AutoGenerateColumns="False"
                                   IsReadOnly="False"
                                   IsBusy="{Binding IsBusy, ElementName=invoiceDetailDomainDataSource}"
                                   CanUserDeleteRows="True"
                                   ShowInsertRow="True"
                                   ShowColumnFooters="True"
                                   Deleted="CommitInvoiceDetailDeleted"
                                   RowEditEnded="CommitInvoiceDetailRowEditEnded"
                                   BeginningEdit="InvoiceDetailBeginningEdit"
                                   ShowGroupPanel="False"
                                   Height="250" Width="550"
                                   >
  <telerik:RadGridView.Columns>
    <telerik:GridViewDataColumn Header="Description" UniqueName="Description" Width="250" IsReadOnly="False"></telerik:GridViewDataColumn>
    <telerik:GridViewMaskedTextBoxColumn Header="Price" UniqueName="Price" Width="80" IsReadOnly="False" MaskType="Numeric" Mask="g"  ></telerik:GridViewMaskedTextBoxColumn>
    <telerik:GridViewMaskedTextBoxColumn Header="Quantity" UniqueName="Quantity" Width="80" IsReadOnly="False" MaskType="Numeric" Mask="g" ></telerik:GridViewMaskedTextBoxColumn>
    <telerik:GridViewExpressionColumn Header="Total" UniqueName="Total" Width="120" IsReadOnly="True" Expression="Price * Quantity">
      <telerik:GridViewExpressionColumn.AggregateFunctions>
        <telerik:SumFunction Caption="Total:" SourceField="Total" ></telerik:SumFunction>
      </telerik:GridViewExpressionColumn.AggregateFunctions>
    </telerik:GridViewExpressionColumn>
  </telerik:RadGridView.Columns>
</telerik:RadGridView>

When i run the code i have an empty grid (no rows displayed) and the groupfooter is empty.
When i remove the AggregateFunctions tag, the rows are displayed without problem.

What am i missing?

[Maya]

Hi peter,

Please take a look at this forum thread for a reference.  

Kind regards,
Maya
the Telerik team

[HDC]

Hello Maya,

Thanks for your response, but there is an extra complication. I'm using the grid as part of a raddataform. I have already posted an issue for this on the forum... it does not work to define an expression row using code when i use the gridview on a dataform.

Please see :
http://www.telerik.com/community/forums/silverlight/data-form/grid-inside-dataform---expression-columns-not-working.aspx

I did not receive a solution as such to this, but rather a workarround (using Expression="Price * Quantity")... which i have demonstrated in the initial code of the thread.

I'm wondering why this code doesn't work (even if you don't place the gridview in a raddataform)... it seems like a straight forward and very basic scenario: create a total column and then calculate a summ on that column. This should not require a dozen lines of code in codebehind!

[Yavor Georgiev]

Hello peter,

 The built-in aggregate functions work with type members (through the SourceField property). If you don't specify a SourceField on the function, the RadGridView will try to infer it from the DataMemberBinding of the column.

 However, as the ExpressionColumn is not a data-bound column, the RadGridView cannot infer a value for the SourceField property of the aggregate function. To remedy this, we have provided the generic AggregateFunction class, which allows you to specify a custom aggregation expression. You can see how it's used in the example attached to the forum thread Maya linked to.

Best wishes,
Yavor Georgiev
the Telerik team