在.net framework 3.5下做的winform程序，在XP下，程序运行时修改app.config成功。在win7下程序运行修改app.config不成功，大家又遇到这种问题的吗？  是系统的原因 还是我程序的原因啊

代码是：string newName = "conn";
                string ProviderName = "System.Data.SqlClient";
                string newConn = "Data Source=" + textBox5.Text.ToString() + "," + textBox1.Text.ToString() + ";Initial Catalog=XtCRM ; User ID=" + textBox3.Text.ToString() + ";Password=" + textBox4.Text.ToString() + "";
                bool isModified = false;
                if (ConfigurationManager.ConnectionStrings["conn"] != null)
                {
                    isModified = true;
                }
                ConnectionStringSettings mysettings = new ConnectionStringSettings(newName, newConn, ProviderName);
                Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
                if (isModified)
                {
                    config.ConnectionStrings.ConnectionStrings.Remove("conn");
                }
                config.ConnectionStrings.ConnectionStrings.Add(mysettings);
                config.Save(ConfigurationSaveMode.Modified);
                ConfigurationManager.RefreshSection("connectionStrings");
                MessageBox.Show("配置成功！");
                Application.Restart();