CODE EXAMPLE FOR CSHARP

Openxml row count

using (SpreadsheetDocument myDoc = SpreadsheetDocument.Open("PATH", true))
 {
   //Get workbookpart
   WorkbookPart workbookPart = myDoc.WorkbookPart;

   //then access to the worksheet part
   IEnumerable<WorksheetPart> worksheetPart = workbookPart.WorksheetParts;

   foreach (WorksheetPart WSP in worksheetPart)
   {
      //find sheet data
      IEnumerable<SheetData> sheetData = WSP.Worksheet.Elements<SheetData>();       
      // Iterate through every sheet inside Excel sheet
      foreach (SheetData SD in sheetData)
      {
           IEnumerable<Row> row = SD.Elements<Row>(); // Get the row IEnumerator
           Console.WriteLine(row.Count()); // Will give you the count of rows
      }
}