error: Some parameters or credentials have not been specified

I have a report with main items and sub-items, the sub-items are rectangles with lists in it. In the initial fase i only get the data for the main items and when a main item toggles a sub-item (rectangle) to visible, i want to load the data for the sub-items from the DB. When the page reloads i get the following error: Some parameters or credentials have not been specified.

protected void rv_Toggle(object sender, System.ComponentModel.CancelEventArgs e)

{

((ReportViewer)sender).LocalReport.DataSources.Clear();

((ReportViewer)sender).LocalReport.DataSources.Add(new Microsoft.Reporting.WebForms.ReportDataSource("MainItems",Objectlist1));

((ReportViewer)sender).LocalReport.DataSources.Add(new Microsoft.Reporting.WebForms.ReportDataSource("SubItems",Objectlist2));

AddReportParameters(((ReportViewer)sender).LocalReport, _SearchFilter);

((ReportViewer)sender).DataBind();

((ReportViewer)sender).LocalReport.Refresh();

}

http://visual-studio.itags.org/q_visual-studio_33627.html