This will be the last Bite Size C# post revolving around CSV and XLS files (for a while at least). The next one will be on a different and probably a bit more exciting topic.

Today we will look at my XLS File Merger, which resides in the Core.XLS namespace of my Core.dll library. It is a static class with one static method MergeFiles. The purpose of this method is to merge 2 or more XLS files into a single file, i.e. taking the worksheets of 2 or more files and combing them into a single file. The MergeFiles method takes 2 arguments: a list of locations of files to be merged (filePathList) and the destination file that will be created (outputFile).

Here is the code:

using System;
using Microsoft.Office.Interop.Excel;

namespace Core.XLS
{
    public static class XlsFileMerge
    {
        public static void MergeFiles(string[] filePathList, string outputFile)
        {
            var app = new Application {Visible = false};

            app.Workbooks.Add("");
            foreach (var file in filePathList)
            {
                app.Workbooks.Add(file);
            }


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

                app.Workbooks[i].Activate();
                for (var j = 1; j <= count; j++)
                {
                    var ws = (_Worksheet) app.Workbooks[i].Worksheets[j];
                    if (ws.UsedRange.Rows.Count <= 1) continue;
                    ws.Select(Type.Missing);
                    ws.Cells.Select();


                    var sel = (Range) app.Selection;
                    sel.Copy(Type.Missing);

                    var sheet = (_Worksheet) app.Workbooks[1].Worksheets.Add(
                        Type.Missing, Type.Missing, Type.Missing, Type.Missing
                                                 );
                    sheet.Name = ws.Name;
                    sheet.Paste(Type.Missing, Type.Missing);
                }
            }
            app.Workbooks[1].SaveAs(@outputFile);
            app.Quit();
        }
    }
}