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using (StreamReader reader = new StreamReader(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "Mainlysoft", "mainlysoft_devassist.txt")))
                {
                    InstallationsPfad = Path.Combine(reader.ReadLine(), "Mainlysoft Devassist");
                    if (InstallationsPfad != "")
                    {
                        // ....

                        x1 = reader.ReadLine();
                        c2 = reader.ReadLine();
                        reader.Close();
                        ReadSuccessful = true;
                    }
                }

                if (ReadSuccessful == true)
                {
                    using (StreamWriter writer = new StreamWriter(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "Mainlysoft", "mainlysoft_devassist.txt")))
                    {
                        writer.WriteLine(InstallationsPfad);
                        writer.WriteLine(x1);
                        writer.WriteLine(c2);
                        writer.WriteLine("update installed");
                        writer.Close();
                    }
                 }