C# WinForms changing database name in other form -

so here first question , first c# program:

i need function permanently change connection string.

my program has structure: main form form1, when click button, options, new - form3, user can log in (password protects changing options) , if login successfull create new form - form4. in constructor of form4, pass sqlconnection object form1. want change database name clicking on button, here code:

var config = configurationmanager .openexeconfiguration(configurationuserlevel.none);  var connectionstringssection = (connectionstringssection)config .getsection("connectionstrings");  var x = connectionstringssection .connectionstrings["app.properties.settings.ppsconnectionstring"] .connectionstring;  string[] words = x.split(';');  words[1] = "initial catalog="+textboxdb.text; x=string.join(";", words);  connectionstringssection .connectionstrings["app.properties.settings.ppsconnectionstring"] .connectionstring = x; //above, variable x in debug mode looks right //i read line below should update file, change permamently config.save(configurationsavemode.modified); configurationmanager.refreshsection("connectionstrings"); 

but doesn't change anything, , have no idea how change settings file user change database name , when restart app, should have new changed connection string.

edit :

thanks responses turns out should run code bin/release .exe version, not under debug in vs , changes config file.

if using visual studio can set range of settings within executable using properties form of project , these settings can accessed without reflection. these properties can made 'application level' or 'user level' determining how wide ranging changes be.

yourprojectname.properties.settings.default.yoursettingname = "a setting";

this if know how many connectionstrings , other variables want store, if require set unknown number of connection strings use datatable rows each setting, can saved xml file in applications directory, or per user.