Using XPath to modify app.config on setup

Sample code to modify the app.config when executing a setup package:

This assumes it is in the "Committed" event of a projectinstaller class. This sample only modifies a connectionString, but can easily be used for anything:

string assemblypath = Context.Parameters["assemblypath"];
string appConfigPath = assemblyPath + ".config";
XmlDocument doc = new XmlDocument();
doc.Load(appConfigPath);
XmlNode aConnection = doc.SelectSingleNode("/configuration/connectionStrings/add[@name=\"aConnectionIdentifier\"]");
aConnection.Attributes["connectionString"].Value = "Data Source=.;Initial Catalog=MyDatabase;User Id=MyUser;Password=MyPassword;";
doc.Save(appConfigPath);