Aggregates of datatables and 3 tier architecture


J

JimLad

Hi,

I have a listview on a page which binds to an objectdatasource which
returns a typed datatable as the select command. There are also
Update, Insert and Delete commands.
I need to display the sum of a couple of these columns and a max and
min of another column.
What is the best way of doing this?

I could:
- Hack around with the listview.
- Run Compute on the datatable.
- Run separate aggregating sproc on the source database.

The middle one seems to be best but I can't see how to get access to
the datatable without causing another call to the database
(essentially calling GetData twice on the tableadapter - once manually
and once thropugh the automated databind). The datatable is not
accessible from the listview or the objectdatasource as far as I can
tell (databind is handled automatically and I don't really want to do
it manually).

Thanks in advance for any help.

James
 
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J

JimLad

Hi,

I have a listview on a page which binds to an objectdatasource which
returns a typed datatable as the select command.  There are also
Update, Insert and Delete commands.
I need to display the sum of a couple of these columns and a max and
min of another column.
What is the best way of doing this?

I could:
- Hack around with the listview.
- Run Compute on the datatable.
- Run separate aggregating sproc on the source database.

The middle one seems to be best but I can't see how to get access to
the datatable without causing another call to the database
(essentially calling GetData twice on the tableadapter - once manually
and once thropugh the automated databind). The datatable is not
accessible from the listview or the objectdatasource as far as I can
tell (databind is handled automatically and I don't really want to do
it manually).

Thanks in advance for any help.

James

Why is it that you spent hours thinking about something and it becomes
clear the moment you put it on a newsgroup? Doh!
The key is the ObjectDataSource.Selected event. e.ReturnValue give you
your datatable or whatever else is the datasource.

Private Sub ObjectDataSource_Selected(ByVal sender As Object,
ByVal e As System.Web.UI.WebControls.ObjectDataSourceStatusEventArgs)
Handles ObjectDataSource.Selected
Dim dataTable As DataTable = CType(e.ReturnValue, DataTable)
TotalLabel.Text = dataTable.Compute("Sum(total)", "").ToString
Dim minEndDateObjectAs Object =
dataTable.Compute("Min(end_date)", "")
If MinEndDateTextBox.Text = "" AndAlso
IsDate(minEndDateObject) Then
MinEndDateTextBox.Text =
CDate(minEndDateObject).ToString("d")
End If
End Sub

James
 

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