GridViewExpressionColumn and Aggregating

[Matthew]

Hi,

How can I add a sumfunction to a GridViewExpression column?
for a GridViewDataColumn I simply add:

<telerik:GridViewDataColumn.AggregateFunctions>
            <telerik:SumFunction />
</telerik:GridViewDataColumn.AggregateFunctions>

and it works 100%, but when I do it for the same for GridViewExpressionColumn:

<telerik:GridViewExpressionColumn.AggregateFunctions>
            <telerik:SumFunction />
 </telerik:GridViewExpressionColumn.AggregateFunctions>

I get an error "No Generic method 'Sum' on type 'System.linq.Enumerable' is compatible with the supplied type arguments".
The data in GridViewDataColumns is of Type Decimal, do i need to set the type of the expression column? if so, how?

thanks.

regards,
Matthew

[Dilyan Traykov]

Hello Matthew,

I'm afraid you cannot explicitly set a data type for a GridViewExpressionColumn, but you could define a generic AggregateFunction as documented in this article. I'm attaching a sample project to better demonstrate how you can implement this.

Please give this a try and let me know if such an approach would work for you.

Regards,
Dilyan Traykov
Telerik by Progress

[Matthew]

Hello Dilyan,

Thanks. Your solution works for me, but please help me understand:
If you have numeric values in the GridViewExpressionColumn, why does the standard sumfunction not work?

Thanks.

regards,
Matthew

[Dilyan Traykov]

Hello Matthew,

The reason the standard sum function does not work when using the GridViewExpressionColumn is that the function is not passed the calculated numeric values, but rather the whole bound objects as that is simply the way this type of column works.

Thus, it cannot operate correctly without an explicit AggregationExpression being provided, which is the case of the custom sum function from the project in my previous reply.

I hope that this clarifies things for you.

Regards,
Dilyan Traykov
Telerik by Progress