将Microsoft.Office.Interop.Excel工作簿保存到MemoryStream不起作用

Question

我有以下方法：

public byte[] CreateBatchFile(string batchId, bool isBatchCandidate, string providerId)
        {
            var currentDate = DateTime.Now;
            var fileName = $"B{batchId}_{providerId}_{"Upgrade"}_{currentDate.Date.ToString().Replace("\\", " ")}_{currentDate.ToShortTimeString().Replace(":", " ")}";

            var agreementItems = this.GetMTNRenewalBatchAgreementItems(batchId, isBatchCandidate, providerId);

            var columnHeadings = new List<string>()
            {
                "MSISDN", "SIM No", "Dealer Code", "Date", "Package Code", "Package Tariff Code", "Action requested", "MTN Done", "MTN Comments"
            };

            Application excel = new Application();
            excel.Visible = false;
            excel.DisplayAlerts = false;
            Workbook workbook = excel.Workbooks.Add(Type.Missing);

            Worksheet worksheet = (Worksheet)workbook.ActiveSheet;
            worksheet.Name = "Renewal Request";
            worksheet.Cells.Font.Size = 15;

            //add column headings
            for (int i = 1; i <= columnHeadings.Count; i++)
            {
                worksheet.Cells[1, i] = columnHeadings[i - 1];
            }

            //row indexer
            int rowCounter = 2;

            //add row data
            for (int i = 1; i <= agreementItems.Count; i++)
            {
                //get the actual agreement item
                var item = agreementItems[i - 1];

                worksheet.Cells[rowCounter, i] = item.Msisdn;
                worksheet.Cells[rowCounter, i] = item.SimNumber;
                worksheet.Cells[rowCounter, i] = currentDate;
                worksheet.Cells[rowCounter, i] = item.ProductCode;
                worksheet.Cells[rowCounter, i] = item.ProviderProductIdentifier;
                worksheet.Cells[rowCounter, i] = "Upgrade";
                worksheet.Cells[rowCounter, i] = "";
                worksheet.Cells[rowCounter, i] = "";

                rowCounter++;
            }

            //add the worksheet to the workbook
            workbook.Worksheets.Add(worksheet);

            MemoryStream ms = new MemoryStream();
            workbook.SaveAs(ms);
            ms.Seek(0, SeekOrigin.Begin);

            byte[] buffer = new byte[(int)ms.Length];
            buffer = ms.ToArray();

            workbook.Close();
            excel.Quit();

            return buffer;
        }

我希望此方法返回一个byte[]，但是问题是，当我将工作簿保存到MemoryStream时，MemoryStream.Length总是显示0。

我在做什么错？