C#

public void Conversion()
        {
            try
            {
                using (sr1 = new StreamReader("c:\\input1.txt"))
                {
                    using (sr2 = new StreamReader("c:\\input2.txt"))
                    {
                        file = new FileStream("c:\\output.txt", FileMode.Create, FileAccess.Write);
                        sw = new StreamWriter(file);
                        string line1;
                        string line2;

                        while ((line1 = sr1.ReadLine()) != null)
                        {
                            string[] temp1 = line1.Split(new char[] { ';' });

                            while ((line2 = sr2.ReadLine()) != null)
                            {
                                string[] temp2 = line2.Split(new char[] { ';' });

                                string final = temp1[0] + ";" + temp1[1] + ";" + temp1[2] + ";" + temp2[2] + ";" + temp1[2] + "-" + temp2[2];
                                sw.WriteLine(final);
                            }
                        }

                    }
                }
            }
            finally
            {
                sr1.Close();
                sr2.Close();
                sw.Close();
                file.Close();
            }
        }