How to get a specific row by worksheet and rowindex in excel file

I need to choose a specific cell in my excel file via using openXML:

Worksheet workSheet = workSheetPart.Worksheet;Cell cell = GetCell(workSheet, "B", 2);private static Cell GetCell(Worksheet worksheet,  string columnName, uint rowIndex)    {        Row row = GetRow(worksheet, rowIndex);        if (row == null)            return null;        return row.Elements<Cell>().Where(c => string.Compare               (c.CellReference.Value, columnName +               rowIndex, true) == 0).First();    }private static Row GetRow(Worksheet worksheet, uint rowIndex)    {        var test = worksheet.GetFirstChild<SheetData>().          Elements<Row>().Where(r => r.RowIndex == rowIndex).First(); //Here is the problem. return worksheet.GetFirstChild<SheetData>().          Elements<Row>().Where(r => r.RowIndex == rowIndex).First();    }

When debugging I have noticed that RowIndex is null, so this is causing the problem I guess in the linq query