How do I merge multiple excel files to a single excel file

Question

Therefore, I was making an Excel sheet aggregator. In my line of business, we occasionally receive a large number of separate Excel files with only one sheet each that are all related.

I partially adopted the concepts from the prior post. But after doing so, I noticed that several of the duplicated excel sheets were empty. only some of them. Why some are blank and others are fine is beyond my comprehension.

The code I employ to access and copy Excel files is shown below.

         OpenFileDialog browse = new OpenFileDialog();
            browse.Multiselect = true;
            DialogResult result = browse.ShowDialog();

            if (result == DialogResult.OK)

                try //try to open it. If its a proper excel file
                {   
                    excel = new Excel.Application();
                    excel.Workbooks.Add("");
                    finalized = excel.Workbooks[1];
                    excel.SheetsInNewWorkbook = 1;
                    for(int i=0; i< browse.FileNames.Length; i++)
                    {
                        excel.Workbooks.Add(browse.FileNames[i]);
                    }
                    //skip the first workbook as it is the finalized one
                    //also note everything in excel starts at 1 and not 0
                    for(int i=2; i<excel.Workbooks.Count; i++)
                    {
                        int count = excel.Workbooks[i].Worksheets.Count;
                        excel.Workbooks[i].Activate();
                        for (int j = 1; j < count; j++)
                        {

                            Excel._Worksheet pastee = (Excel._Worksheet)excel.Workbooks[i].Worksheets[j];
                            Excel._Worksheet sheet = (Excel._Worksheet)finalized.Worksheets.Add(Type.Missing, Type.Missing, Type.Missing, Type.Missing);
                            //Excel._Worksheet sheet = finalized.Sheets[1];
                            pastee.Copy(Before: sheet);


                        }//end of for j
                    }//end of for i
                }//end of try

Here is the code I use to save the excel file

            SaveFileDialog browse = new SaveFileDialog();
            browse.Title = "Save as Excel";
            browse.Filter = "Excel workbook | *.xlsx";
            DialogResult result = browse.ShowDialog();

            finalized.SaveAs(browse.FileName, Excel.XlFileFormat.xlWorkbookDefault);

            MessageBox.Show("Success", "Message");
            //unlock the file
            Global.releaseComObjects(finalized, excel);

Answer 1

You copy a worksheet from before each source sheet and add a new worksheet to your "finalised" workbook (the "sheet") in your inner loop. Because you actually create two sheets for each source sheet, every "sheet" created by your Add command will be empty. Another issue is that, as you pointed out, Excel's arrays are 1-based; hence, you must loop until j >= count rather than j count.

So I think that code would work better:

Excel.Worksheet dummy = finalized.Worksheets[1];

for (int i = 2; i <= excel.Workbooks.Count; i++)
{
    int count = excel.Workbooks[i].Worksheets.Count;

    for (int j = 1; j <= count; j++)
    {
        Excel._Worksheet pastee = (Excel._Worksheet)excel.Workbooks[i].Worksheets[j];
        pastee.Copy(dummy);
    }
}

dummy.Delete();