I have successfully implemented a custom provider for RadSpreadsheet following the example here: http://www.telerik.com/support/code-library/spreadsheetdatabaseprovider.
I would like to be able to update a RadLabel on the same webform with some data derived from the saved sheet (for example, the count of rows). I have passed a reference to the RadLabel into the constructor of the custom provider and am setting it there:
PerformanceSheetProvider : SpreadsheetProviderBase
_resultLabel = resultLabel;
_resultLabel.Text = workbook.Sheets.Rows.Count.ToString();
However, the RadLabel value is not updated. I have also tried refreshing the update panel in which the label is contained in the client-side override of _onCallbackResponse:
"<%= RadAjaxPanel2.ClientID %>"
...but the label is still not updated.