Thank you for contacting Syncfusion support.
We have analayzed query and we are not able to understand your exact scenorio. So could you please share more details like in which value do you want to show in Tooltip for each row(Record , Group caption row) .
Please let us know if you have any questions.
We have analyzed your issue, there is no corresponding record for the row index when you expand the row. It is the cause of exception. You can get the record by using Record API. You can refer the below codesnippet.
void OnQueryCellInfo(object sender, GridQueryCellInfoEventArgs e)
var style = e.Style as GridDataStyleInfo;
var data = style.CellIdentity;
var record = data.Record as Customers;
We have prepared a sample based on this. Please find the attached sample below.
Please let us know if you need further assistance.