How to reload an assembly for a .NET Application Domain?

Question

We are loading an assembly (a DLL) which reads a configuration file. We need to change the configuration file and then re-load the assembly. We see that after loading the a

Answer 1

If you are just changing some sections you can use ConfigurationManager.Refresh("sectionName") to force a re-read from disk.

static void Main(string[] args)
    {
        var data = new Data();
        var list = new List<Parent>();
        list.Add(new Parent().Set(data));

        var configValue = ConfigurationManager.AppSettings["TestKey"];
        Console.WriteLine(configValue);

        Console.WriteLine("Update the config file ...");
        Console.ReadKey();

        configValue = ConfigurationManager.AppSettings["TestKey"];
        Console.WriteLine("Before refresh: {0}", configValue);

        ConfigurationManager.RefreshSection("appSettings");

        configValue = ConfigurationManager.AppSettings["TestKey"];
        Console.WriteLine("After refresh: {0}", configValue);

        Console.ReadKey();
    }

(Note that you have to change the application.vshost.exe.config file if you are using the VS hosting process, when testing this.)

Answer 2

You can't unload an assembly once it's been loaded. However, you can unload an AppDomain, so your best bet would be to load the logic into a separate AppDomain and then when you want to reload the assembly you'll have to unload the AppDomain and then reload it.

Answer 3

Please see the following 2 links for an answer:

• Dynamic Plugins by Jon Shemitz
• Using AppDomain to load and unload dynamic assemblies by Steve Holstad

Answer 4

I believe the only way to do this is to start a new AppDomain and unload the original one. This is how ASP.NET has always handled changes to web.config.