Write in app.config file in C#

You can use this function to save permanent value in Config file...
 
 public static void WriteSetting(string key, string value)
        {
            ////load config document for current assembly
            XmlDocument doc = loadConfigDocument();
            // retrieve appSettings node
            XmlNode node = doc.SelectSingleNode("//appSettings");
            if (node == null)
            {
                throw new InvalidOperationException("appSettings section not found in config file.");
            }
            try
            {
                // select the 'add' element that contains the key
                XmlElement elem = (XmlElement)node.SelectSingleNode(string.Format("//add[@key='{0}']", key));
                if (elem != null)
                {
                    // add value for key
                    elem.SetAttribute("value", value);
                }
                else
                {
                    // key was not found so create the 'add' element
                    // and set it's key/value attributes
                    elem = doc.CreateElement("add");
                    elem.SetAttribute("key", key);
                    elem.SetAttribute("value", value);
                    node.AppendChild(elem);
                }
                doc.Save(getConfigFilePath());
            }
            catch
            {
                throw;
            }
        }
        public static XmlDocument loadConfigDocument()
        {
            XmlDocument doc = null;
            try
            {
                doc = new XmlDocument();
                doc.Load(getConfigFilePath());
                return doc;
            }
            catch (System.IO.FileNotFoundException e)
            {
                throw new Exception("No configuration file found.", e);
            }
        }
        public static string getConfigFilePath()
        {
            return Assembly.GetExecutingAssembly().Location + ".config";
        }
 
Also you can read my artical on this site about all of this.

The following function can Save value in config file........
 public static void SaveSetting(string ConnectionString1)
        {
            System.Configuration.Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            config.AppSettings.Settings.Remove("SqlConnectionADODB");
            config.AppSettings.Settings.Add("SqlConnectionADODB", ConnectionString1);
            config.Save();
            ConfigurationManager.RefreshSection("appSettings");
        }

hi

You can edit windows App.config file. hope below link give your solution.

http://www.codeproject.com/KB/cs/SystemConfiguration.aspx

thanks
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