How to append connectionString from one config file to other config file

[C# Programming]

Hi,

I'm trying to copy connectionStrings from C:\test2\web.config to c:\test1\app.config. In web.config, connectionString element looks as below. both config files are not belong to my project.

ExeConfigurationFileMap fileMap = new ExeConfigurationFileMap(); fileMap.ExeConfigFilename = @"c:\test1\app.config";Configuration config = ConfigurationManager.OpenMappedExeConfiguration(fileMap, ConfigurationUserLevel.None); var connectionStringsSection = (ConnectionStringsSection)config.GetSection("connectionStrings"); ExeConfigurationFileMap fileMapWeb = new ExeConfigurationFileMap();fileMapWeb.ExeConfigFilename = @"C:\test2\web.config";Configuration configWeb = ConfigurationManager.OpenMappedExeConfiguration(fileMapWeb, ConfigurationUserLevel.None); var connectionStringsWeb = (ConnectionStringsSection)configWeb.GetSection("connectionStrings"); //here I got connectionString element in connectionStringsWeb from web.config file. But how to append this connectionString element to app.config file.
Thanks in advance.