Setting a registry value based on dialog in a visual studio setup project

I have visual studio setup project with a custom RadioButtons dialog.

How do I get it to write the value of the ButtonProperty in the registry after it is selected in the UI?

If using a .Net Installer class do the following:

1. Pipe the data through to your Custom Action using CustomActionData eg: If your property is called MYPROP: /MyVar=[MYPROP]

2. You can now access the data from your installer class:

   protected override void OnAfterInstall(IDictionary savedState) {
   
           string myVar = Context.Parameters["MyVar"];
           RegistryKey key = Registry.LocalMachine;
           using (key = key.CreateSubKey(@"SOFTWARE\MyCompany\MyApp")) {
               key.SetValue("MyVar", myvar);
               key.Close();
           }
   }