如何使用OpenXmlAttribute更改字体大小？

using DocumentFormat.OpenXml;
using DocumentFormat.OpenXml.Spreadsheet;
using DocumentFormat.OpenXml.Packaging;

public void ChangeFontSize(string spreadsheetFileName, string sheetName, string cellReference, double fontSize)
{
    using (SpreadsheetDocument spreadsheetDocument = SpreadsheetDocument.Open(spreadsheetFileName, true))
    {
        WorkbookPart workbookPart = spreadsheetDocument.WorkbookPart;
        WorksheetPart worksheetPart = workbookPart.WorksheetParts.FirstOrDefault(wp => wp.PartName.ToString().EndsWith(sheetName));

        if (worksheetPart != null)
        {
            Cell cell = worksheetPart.Worksheet.Descendants<Cell>().FirstOrDefault(c => c.CellReference == cellReference);

            if (cell != null)
            {
                RunProperties runProperties = new RunProperties();
                FontSize fontSizeElement = new FontSize() { Val = fontSize.ToString() };
                runProperties.Append(fontSizeElement);

                Text text = new Text() { Text = "Your text here" };
                Run run = new Run();
                run.Append(runProperties);
                run.Append(text);

                CellValue cellValue = new CellValue() { Text = "Your text here" };
                cell.CellValue = cellValue;
                cell.DataType = new EnumValue<CellValues>(CellValues.SharedString);

                worksheetPart.Worksheet.Descendants<Row>().FirstOrDefault(r => r.RowIndex == GetRowIndex(cellReference)).AppendChild(cell);

                worksheetPart.Worksheet.Save();
            }
        }
    }
}

private uint GetRowIndex(string cellReference)
{
    Regex regex = new Regex(@"\d+");
    Match match = regex.Match(cellReference);
    return uint.Parse(match.Value);
}