如何使用C# winforms将excel档案转换为pdf格式？

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

private void ConvertToPDFButton_Click(object sender, EventArgs e)
{
    // 选择Excel文件
    OpenFileDialog openFileDialog = new OpenFileDialog();
    openFileDialog.Filter = "Excel文件|*.xlsx;*.xls";
    if (openFileDialog.ShowDialog() == DialogResult.OK)
    {
        string excelFilePath = openFileDialog.FileName;

        // 创建Excel应用程序对象
        Excel.Application excelApp = new Excel.Application();
        Excel.Workbook excelWorkbook = excelApp.Workbooks.Open(excelFilePath);
        Excel.Worksheet excelWorksheet = excelWorkbook.Sheets[1];

        // 将Excel文件保存为PDF
        string pdfFilePath = excelFilePath.Replace(".xlsx", ".pdf").Replace(".xls", ".pdf");
        excelWorksheet.ExportAsFixedFormat(Excel.XlFixedFormatType.xlTypePDF, pdfFilePath);

        // 关闭Excel应用程序
        excelWorkbook.Close();
        excelApp.Quit();

        MessageBox.Show("转换完成！PDF文件路径：" + pdfFilePath);
    }
}