[]
Returns an IRange representing the area of the current IRange which is iteratively grown as needed until it includes no partial merged cells.
IRange EntireMergeArea { get; }
ReadOnly Property EntireMergeArea As IRange
worksheet.Range["A1:B2"].Merge();
IRange mergeArea = worksheet.Range["A1"].EntireMergeArea;
int rowCount = mergeArea.RowCount;