How to merge several sheets of excel file into one?

Question

C++ / C#

In general, the essence is this in an excel file of about 100 sheets, in each sheet you need to copy a certain piece and paste everything into another excel file in one sheet, I got such a non-working shit code

class Program
    {
        static void Main(string[] args)
        {
            Excel.Application input = new Excel.Application();
            Excel.Application output = new Excel.Application();
            input.Workbooks.Open(@"C:\Users\sharov\Desktop\main.xls");
            output.Workbooks.Open(@"C:\Users\sharov\Desktop\temp.xlsx");
            Excel.Worksheet outSheet = (Excel.Worksheet)output.ActiveWorkbook.Worksheets[1];
            int i = 1;
            foreach (Excel.Worksheet sheet in input.ActiveWorkbook.Worksheets)
            {
                Excel.Range excelcells = sheet.get_Range("J7","DW63");
                foreach(Excel.ListRow row in excelcells)
                    outSheet.Rows[i++] = row;
            }

            input.Quit();
            output.ActiveWorkbook.Saved = true;
            output.Quit();
        }

    }

Answer 1

Firstly, there is no need to open two Excel - open spreadsheets in one and work with them. Workbooks.Open just returns you a Workbook object.
From the source, select Range and do Copy
. In the resulting one, go to the end and do Paste or PasteSpetial.

Answer 2

I used to work with documents through Microsoft.Office.Interop.Excel, I didn't like it. For each document, there is an instance of Excel in memory, everything is tossing and turning, incomprehensible errors.
Now I use EPPlus, I have enough with my head. Look here: https://epplus.codeplex.com/ , https://github.com/ylatuya/EPPlus
Examples here: https://epplus.codeplex.com/wikipage?title=FAQ&ref...
The library is intuitive.