我想使用C#将.xls or.xlsx文件转换为.csv格式

using System;
using Excel = Microsoft.Office.Interop.Excel;

public class ExcelToCsvConverter
{
    public void ConvertToCsv(string excelFilePath, string csvFilePath)
    {
        Excel.Application excelApp = new Excel.Application();
        Excel.Workbook excelWorkbook = excelApp.Workbooks.Open(excelFilePath);
        Excel.Worksheet excelWorksheet = excelWorkbook.Sheets[1];

        Excel.Range excelRange = excelWorksheet.UsedRange;
        int rowCount = excelRange.Rows.Count;
        int columnCount = excelRange.Columns.Count;

        System.IO.StreamWriter csvFile = new System.IO.StreamWriter(csvFilePath);

        for (int row = 1; row <= rowCount; row++)
        {
            string csvRow = "";
            for (int column = 1; column <= columnCount; column++)
            {
                if (column != 1)
                {
                    csvRow += ",";
                }
                csvRow += "\"" + excelRange.Cells[row, column].Value.ToString() + "\"";
            }
            csvFile.WriteLine(csvRow);
        }

        csvFile.Close();

        excelWorkbook.Close();
        excelApp.Quit();
    }
}