public static class MyClass
{
   public static void Method1(bool flag)
   {
    if (flag) {
     //Надо запустить Method2 в том же потоке
    }
    else {
     //Надо запустить Method2 в отдельном домене
     AppDomainSetup ads = new AppDomainSetup();
     AppDomain ad2 = AppDomain.CreateDomain("New Domain", null, ads);
     Starter mbrt = 
                (Starter) ad2.CreateInstanceAndUnwrap(Assembly.GetEntryAssembly().FullName,
                                                               typeof(Starter).FullName);
     mbrt.Runner(objTClist);
    }
   }
   public static void Method2
   {
   }
}

class Starter : MarshalByRefObject
{
    public void Runner
    {
        MyClass.Method2();
    }
}

class Program
    {
        static void Main(string[] args)
        {
            AppDomain another = AppDomain.CreateDomain("Another appDomain");
            another.DoCallBack(Hello);
        }

        static void Hello()
        {
            Console.WriteLine("Hello from " + AppDomain.CurrentDomain.FriendlyName);
        }
    }

K>class Program
K>    {
K>        static void Main(string[] args)
K>        {
K>            AppDomain another = AppDomain.CreateDomain("Another appDomain");
K>            another.DoCallBack(Hello);
K>        }

K>        static void Hello()
K>        {
K>            Console.WriteLine("Hello from " + AppDomain.CurrentDomain.FriendlyName);
K>        }
K>    }
K>

public void DoCallBack (
    CrossAppDomainDelegate callBackDelegate
)

otherDomain.DoCallBack(new CrossAppDomainDelegate(MyCallBack));

otherDomain.DoCallBack(new CrossAppDomainDelegate(MyCallBack));
otherDomain.DoCallBack(MyCallBack);
otherDomain.DoCallBack(delegate { /*.....*/ });

K>>otherDomain.DoCallBack(new CrossAppDomainDelegate(MyCallBack));
K>>otherDomain.DoCallBack(MyCallBack);
K>>otherDomain.DoCallBack(delegate { /*.....*/ });

K>>

otherDomain.DoCallBack(delegate { MyCallBack(prm1, prm2, ... ); } );

AppDomainSetup ads = new AppDomainSetup();
AppDomain ad2 = AppDomain.CreateDomain("New Domain", null, ads);
ad2.DoCallBack(delegate {ExecuteTestCaseInThread(objTClist); } );

G>>AppDomainSetup ads = new AppDomainSetup();
G>>AppDomain ad2 = AppDomain.CreateDomain("New Domain", null, ads);
G>>ad2.DoCallBack(delegate {ExecuteTestCaseInThread(objTClist); } );
G>>

[Serializable]
public static class BHTestLoader
{
    public static void ExecuteTC(object objTClist)
    {
        switch (options.RunningStyle) {
            case RunningStyles.SingleThread:
                bgThread = new Thread(new ParameterizedThreadStart(ExecuteTestCaseInThread));
                break;
            case RunningStyles.SingleDomain:
                bgThread = new Thread(new ParameterizedThreadStart(ExecuteTestCaseInDomain));
                break;
        }
        bgThread.Start(objTClist);
    }
    public static void ExecuteTestCaseInThread(object objTClist)
    {
        List<TestCase> TClist = new List<TestCase>();
        if (objTClist as List<TestCase> != null) {
            TClist = objTClist as List<TestCase>;
        }
        else {
            TestCase atc = objTClist as TestCase;
            TClist.Add(atc);
        }
        List<string> AssemblyPathList = new List<string>();
        foreach (TestCase tc in TClist) {
            if (!AssemblyPathList.Contains(tc.AssemblyPath)) {
                AssemblyPathList.Add(tc.AssemblyPath);
            }
        }
        
        FireExecuteStateChanged(ExecuteStates.Run);
        foreach (string path in AssemblyPathList) {
            List<TestCase> li = new List<TestCase>();
            foreach (TestCase tc in TClist) {
                if (tc.AssemblyPath == path) {
                    li.Add(tc);
                }
            }
            ExecuteTestMethods(li);
        }
    }
    private static void ExecuteTestCaseInDomain(object objTClist)
    {
        AppDomainSetup ads = new AppDomainSetup();
        AppDomain ad2 = AppDomain.CreateDomain("New Domain", null, ads);
        ad2.DoCallBack(delegate {ExecuteTestCaseInThread(objTClist); } );
         bgThread.Abort();
    }

}

ad2.DoCallBack(delegate {ExecuteTestCaseInThread(objTClist); } );

G>>>AppDomainSetup ads = new AppDomainSetup();
G>>>AppDomain ad2 = AppDomain.CreateDomain("New Domain", null, ads);
G>>>ad2.DoCallBack(delegate {ExecuteTestCaseInThread(objTClist); } );
G>>>

Apply the SerializableAttribute attribute to a type to indicate that instances of this type can be serialized. The common language runtime throws SerializationException if any type in the graph of objects being serialized does not have the SerializableAttribute attribute applied.

ad2.DoCallBack(delegate {ExecuteTestCaseInThread(objTClist); } );