how to do this aggregate?

[Henry]

three columns in the grid, I want to the aggregate value in the third column = sum(first column) / sum(second column) -1, and show it in percentage. I guess this has to be done in the code behide, how to wire that?

Thanks.

[Jayesh Goyani]

Hello Henry,

Please check below code snippet.

<telerik:GridCalculatedColumn HeaderText="Total"  DataType="System.Double"
                       DataFields="Column1, Column2"  Expression="({0}/{1})-1"
                       Aggregate="Avg" />

Note : if you want to sum then use Aggregate="Sum" in above code.

Thanks,
Jayesh Goyani

[Henry]

Jayesh,

1).somewho I can't add the calculated column in the grid, whenever I add it, the page failed to load and show exception on another column(which works fine without calculated column. the error is below, where 'XXXX' is the class that bind to the grid.

Unable to cast object of type 'DynamicClass1' to type 'XXXX'.

2). to do the custom aggregate in the code behind, I found this http://demos.telerik.com/aspnet-ajax/grid/examples/generalfeatures/aggregates/defaultcs.aspx, the question is that in the example, the result is assigned to "e.Result", what if there two more than one custom aggregate? how do we know which column is the e.Result point to?

Thanks.

[Henry]

still not sure about what happen on 1.

for 2, I've figure it out. 

thanks.