Inserting object into excel using c#

Hi, try this:

string folder1 = @"C:\Folder 1";
string folder2 = @"C:\Folder 2";
 
ExcelFile excelFile = new ExcelFile();
ExcelWorksheet excelSheet = excelFile.Worksheets.Add("Sheet1");
 
excelSheet.Cells[0, 0].Value = "File Mask";
excelSheet.Cells[0, 1].Value = "Input";
excelSheet.Cells[0, 2].Value = "Output";
 
string[] textFiles =  Directory.GetFiles(folder1, "*.txt");
for (int i = 0; i < textFiles.Length; i++)
{
    excelSheet.Cells[1 + i, 0].Value = Path.GetFileNameWithoutExtension(textFiles[i]).Replace("_input", "");
    excelSheet.Cells[1 + i, 1].Value = Path.GetFileName(textFiles[i]);
}
 
textFiles = Directory.GetFiles(folder2, "*.txt");
for (int i = 0; i < textFiles.Length; i++)
    excelSheet.Cells[1 + i, 2].Value = Path.GetFileName(textFiles[i]);
 
excelFile.Save(@"C:\Book1.xlsx");

I'm not 100% sure if this is what you need but at least it will give you a good starting point.
Note that I used this .NET component for excel files and as you may notice it has an easy to use interface for creating an excel's workbook with C#.