Jails is a framework for .NET that simplifies the task of running code in an isolated environment. It comes bundled with an AppDomain isolator which lets you sandbox code in a separate AppDomain.

Currently, it supports two ways of interacting with your sandboxed class. Either through a dynamic proxy, or a typed proxy. The typed proxy lets you specify an interface that acts as a strongly typed proxy.

It is currently in early alpha and may or may not support your specific use case. Please create an issue if you feel something is wrong or missing.

Install-Package Jails

// Create the AppDomain isolator. By default it only gives the "Execute"
// permission.
var isolator = new AppDomainIsolator();

// Create an environment and register an assembly name with it.
// This will load the assembly in our jailed domain.
var environment = new DefaultEnvironment();
environment.Register(@"C:\Temp\UntrustedAssembly.dll");

using(var jail = Jail.Create(isolator, environment))
{
    // Create a real dynamic proxy which will forward any calls to the
    // internally created instance of "Some.Untrusted.Class".
    dynamic proxy = jail.Resolve("Some.Untrusted.Class");

    // Invoke the method "Run" passing two arguments. Both method name and
    // argument types must match "Some.External.Class".
    string result = proxy.Run("argument1", 2);

    Console.WriteLine(result);
}

For more information, see the wiki

• Why use Jails? Sandboxing code can sometimes be tricky. It doesn't have to be, but Jails try to provide a layer of abstraction on top of sandboxes built with AppDomains and processes.
• Why strong naming? Strong naming Jails is done to be able to give it full trust in the jailed domain. I know of no other way to accomplish this.