Merge multi files into single file.

Code below will merge the multiple files into single file. This will work in C# 4.0 framework on wards. tempFiles is the string , holding the filepath+name of the files . Between each files a separator',' is present. 

            string[] split = tempFiles.Split(',');
            string export_file = "MergedFiles.txt";
            File.WriteAllLines(filePath + export_file, split.SelectMany(File.ReadLines));