Question

I have a bit of f# code (below) that takes a unit->obj and evaluates it in its own appdomain. The motivation is that I need to free assemblies loaded during the evaluation. The code appears to work fine, at least on the trivial examples I have tried. However, it fails with an exception when called from an NUnit test. The exception and code are below. I’ll be most grateful for any help.

Sandbox.trivial_test:
System.Runtime.Serialization.SerializationException : Type is not
resolved for member ‘Sandbox+myDelegate@28,sandboxtest,
Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’.

module Sandbox

open System

type IsolationRunner (f:unit->obj) = 
    inherit System.MarshalByRefObject ()

    let mutable storedResult : obj option = None

    member x.callback () : unit =
       let res = f ()
       storedResult <- Some res

    member x.result : obj =
       match storedResult with
         None -> failwith "No result yet"
       | Some x -> x

let run_code_in_own_appdomain (f: unit -> obj) : obj =        
        let appDomain = AppDomain.CreateDomain "MyTempDomain"
        try
            let ir = IsolationRunner f
            let myDelegate = new CrossAppDomainDelegate (fun () -> ir.callback ())
            appDomain.DoCallBack myDelegate
            ir.result
        finally
            AppDomain.Unload appDomain


open NUnit.Framework

[<Test>]
let trivial_test () =
    let actual = run_code_in_own_appdomain (fun x -> 123 |> box) |> unbox
    printf "result is %O\n" actual
    Assert.AreEqual (123, actual)

Answer 1

The kind netizens of NUnit-Discuss suggested a solution. Briefly, just let path be the location (i.e. directory) of the executable, then create the other domain as:

AppDomain.CreateDomain (“MyTempDomain”, null, path, “”, false)