How do the Built in Footer Aggregate Functions Work?

[Billy]

I can tell a column to do a sum of all its values and the sum will be displayed in the footer fo the grid. How exactly does the grid do this? Is it using Linq? I ask because I need to do a custom aggregate, and in order to do this custom aggregate i need all of the values in the column for each group.

For example, if I could do something along the lines of "select all values from rad grid where column = e.column and group =  ??" that would be great. As you can see I'm not really sure how to know what group I am in either. I've seen examples using looping in the PreRender event but how can this be done in the CustomAggregate event?

Thanks!

[Shinu]

Hi Billy Hasan,

I suppose you have grouping enabled in your grid, and so if you want to add custom group footer aggregate, then you can try the following code.

ASPX:

 . . .
<telerik:GridBoundColumn DataField="Number" Aggregate="Custom" DataType="System.Int64" HeaderText="Number"
    SortExpression="Number" UniqueName="Number">
</telerik:GridBoundColumn>
 . . .

C#:

protected void RadGrid1_CustomAggregate(object sender, GridCustomAggregateEventArgs e)
{
    if (e.Item is GridGroupFooterItem && e.Column.UniqueName == "Number") // When grouping is enabled
    {
        if (RadGrid1.MasterTableView.GroupByExpressions.Count != 0)
        {
            int gIndex = Convert.ToInt32(e.Item.GroupIndex)/2;
            GridGroupHeaderItem hItem = (GridGroupHeaderItem)RadGrid1.MasterTableView.GetItems(GridItemType.GroupHeader)[gIndex];
            GridItem[] items = hItem.GetChildItems();
            int result = 0;
            foreach (GridDataItem item in items)
            {
                result = Convert.ToInt32(item["Number"].Text) + result;
            }
            e.Result = result.ToString();
        }
    }
    if (e.Item is GridFooterItem && e.Column.UniqueName == "Number") // When grouping is not enabled
    {
        int result=0;
        foreach (GridDataItem item in RadGrid1.MasterTableView.Items)
        {
            result = Convert.ToInt32(item["Number"].Text) + result;
        }
        e.Result = result.ToString();
    }
}

-Shinu.

[Billy]

Thanks for the info, I ended up keeping track of the values in OnItemDataBound and then doing what I needed to do in the CustomAggregate event.

So I guess no sweet way to use Linq against the grid then? Still curious how the internals work for the sum, avg, etc. functions work.

[nFocus]

This worked super until I realized that it didn't work when I needed the RadGrid to do paging.  Back to the drawing board.

.... I went back to the drawing board and realized that the built in aggregates work the same way.  The example by Shinu worked fine but I would note that e.Item.GroupIndex is a string, not an int.  If you group by two or more different columns then !bang! "Input string in wrong format" due to the x_y_z_... format when grouping.  Thanks for the lead though!