如何通过使用Excel Interop添加新工作表来覆盖现有Excel文件-C＃

Question

My program, every hour, does some math calculations and saves these result into excel. When it first run(lets say 08:00 AM) it creates a excel workbook and one sheet namely "Sheet1". It saves excel and releases the COM objects. so far everything is fine.

My problem begins with second run (09:00 AM). when it tries to save new results, it overwrites existing excel file (This is OK, the way i want it) but it overwrites Sheet1 which was created in 08:00 AM. I want it to save new result in Sheet2.

In third run, i want it to save result in Sheet3
In fourth run, i want it to save result in Sheet4. so on so forth..

How can i change my code to do like above ? thanks in advance..

My Code:

using excelApp = Microsoft.Office.Interop.Excel;

public static void Main(string[] arg)
    {
        while (true)
        {               
            writeToExcel();
            int wait = 3600 * 1000;
            System.Threading.Thread.Sleep(Convert.ToInt32(wait));
        }
    }
public static void writeToExcel()
    {
        excelApp.Application excl = new Microsoft.Office.Interop.Excel.Application();
        excl.Visible = true;

        //MATH CALCULATIONS...... 

        excelApp.Workbook wb = excl.Workbooks.Add(excelApp.XlWBATemplate.xlWBATWorksheet);
        excelApp.Worksheet ws1 = (excelApp.Worksheet)wb.Worksheets[1];
        excelApp.Worksheet ws2 = (excelApp.Worksheet)wb.Sheets.Add();
        excelApp.Worksheet ws3 = (excelApp.Worksheet)wb.Sheets.Add();
        excelApp.Worksheet ws4 = (excelApp.Worksheet)wb.Sheets.Add();
        excelApp.Worksheet ws5 = (excelApp.Worksheet)wb.Sheets.Add();
        excl.DisplayAlerts = false;
        string fileName = string.Format(@"{0}\Data_" + DateTime.Now.Month + "-" DateTime.Now.Day  + ".xlsx", Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory));
        workSheet.SaveAs(fileName);
        Console.WriteLine("Excel Saved Successfully!!");

        excl.Quit();

        // Release COM objects
        if (excl != null)                                       
        System.Runtime.InteropServices.Marshal.ReleaseComObject(excl);

        if (workSheet != null)                   
        System.Runtime.InteropServices.Marshal.ReleaseComObject(workSheet);

        excl = null;
        workSheet = null;

        GC.Collect();
}

Answer 1

You need to get the work book from the saved file. So at the beginning of your routine, you need a mechanism to determine if today's file already exists, if so, use the the following to get your Workbook.

        Workbook WB = ExcelApp.Workbooks.Open(fileName, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing,
            Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);

Hopefully this helps you see the error in your ways.