Create custom AppDomain and add assemblies to it

Question

How can I create an appdomain, add assemblies to it, then destroy that app domain? This is what I have tried:

    static void Main(string[] args)
    {           
        string pathToExe = @"A:\Users\Tono\Desktop\ConsoleApplication1.exe";

        AppDomain myDomain = AppDomain.CreateDomain("MyDomain");

        Assembly a = Assembly.Load(System.IO.File.ReadAllBytes(pathToExe));

        myDomain.Load(a.FullName); // Crashes here!            
    }

I have also tried:

myDomain.Load(File.ReadAllBytes(pathToExe)); 

how can I add an assembly to the appdomain. Once I do that I can find the method via reflection execute it and then destroy the appdomain

The exception that I get is:

Could not load file or assembly 'ConsoleApplication1, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.

Florinda

It is easier to load assembly to your own domain - so instead of trying to push assembly into other domain consider running some code in other domain to load whatever assembly you want (don't forget that you may need to pre-load dependencies or setup assembly search path correctly). – Microcrystalline

"Or one of its dependencies" is the usual problem. Use Fuslogvw.exe if you have no idea what that might be. And use AppDomainSetup to set the correct private path. – Division

Answer 1

Two quick points:

1. AppDomain.Load loads an assembly in the current AppDomain and not on myDomain (weird, I know).
2. AppDomain.Load loads an assembly in the Load context, which resolves assemblies from the apps base-dir, the private-bin-paths and the GAC. Most probably, the assembly you try to load is not located in any of these locations which explains the exception message.

For more info have a look at this answer.

One way to load assemblies to an AppDomain is by creating a MarshalByRef-derived loader. You need something like this to avoid leaking types (and assemblies) to your main AppDomain. Here's a simple one:

public class SimpleAssemblyLoader : MarshalByRefObject
{
    public void Load(string path)
    {
        ValidatePath(path);

        Assembly.Load(path);
    }

    public void LoadFrom(string path)
    {
        ValidatePath(path);

        Assembly.LoadFrom(path);
    }

    private void ValidatePath(string path)
    {
        if (path == null) throw new ArgumentNullException("path");
        if (!System.IO.File.Exists(path))
            throw new ArgumentException(String.Format("path \"{0}\" does not exist", path));
    }
}

And use it like that:

//Create the loader (a proxy).
var assemblyLoader =  (SimpleAssemblyLoader)myDomain.CreateInstanceAndUnwrap(typeof(SimpleAssemblyLoader).Assembly.FullName, typeof(SimpleAssemblyLoader).FullName);
//Load an assembly in the LoadFrom context. Note that the Load context will
//not work unless you correctly set the AppDomain base-dir and private-bin-paths.
assemblyLoader.LoadFrom(pathToExe);

//Do whatever you want to do.

//Finally unload the AppDomain.
AppDomain.Unload(myDomain);

Gaudette

Hello, I just tried to use your suggestion to kind of preload some .net assemblys to find out if they contain a certain interface class implementation. But in contrast to loading the assembly into the current domain, which works fine, i cannot load them into my newly created AppDomain myDomain. – Additory