How do I save parameters before closing my Windows Phone Runtime app and use these parameters when I activate my app? I have a String and an int that I need to save.
You can use LocalSettings for that.
Use below code to save values in to the settings
Windows.Storage.ApplicationDataContainer localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;
localSettings.Values["exampleSetting"] = "test";
to retrieve settings use below code
var value = localSettings.Values["exampleSetting"] as string;
More details available here