If you are using Infragistics DataGrid, the Excel export default is related to page size, 500 rows. To Export all rows, need to disable Pager, then bind data to the grid again, then call the export function. Review the Row count from Add Watch to assure the count is correct.
[![Protected Sub WebImageButton1_Click(sender As Object, e As ButtonEventArgs) Handles WebImageButton1.Click
WebDataGrid1.Behaviors.Paging.Enabled = False
WebDataGrid1.DataBind()
WebExcelExporter1.Export(WebDataGrid1)
WebDataGrid1.Behaviors.Paging.Enabled = True
End Sub][1]][1]