public class Foo<T>
{
    protected class Private2 : Private1<Foo<T>>
    { }

    protected class Private1<T2> where T2 : Foo<T>
    {
        public sealed class Nested
        {
            public void Test(T2 foo)
            {
                foo.Method2(this); //Nope!
                var nes = (Private2.Nested)this; //Nope!
            }
        }
    }

    public void Method1()
    {
        var nested = new Private2.Nested();
        nested.Test(this);
    }

    private void Method2(Private2.Nested nested)
    {
        // something code...
    }
}

public class Bar<GoodName, OtherName, Readability, NopeMr, DontThinkSo, Suffering, Dispair>
{
    //If only this was real...
    using BarT = Bar<GoodName, OtherName, Readability, NopeMr, DontThinkSo, Suffering, Dispair>;

    public void Method1(BarT bar) { ... } //so good!!

    //goodbye readability... see you never...
    public void Method2(Bar<GoodName, OtherName, Readability, NopeMr, DontThinkSo, Suffering, Dispair> whatIsThisVariable) { ... }
}

public class Base {
    public static int Value;
    public class Nested { }
}
public class Derived:Base { }

public static void Test() {
    Derived.Value=10;
    Console.WriteLine(Base.Value);
    Base.Value=20;
    Console.WriteLine(Derived.Value);
    Base.Nested bn=new Derived.Nested();
    Derived.Nested dn=new Base.Nested();
    Console.WriteLine(typeof(Base.Nested).FullName);
    Console.WriteLine(typeof(Derived.Nested).FullName);
    Console.WriteLine(typeof(Base.Nested)==typeof(Derived.Nested));
}

public class Foo<T>
{
    private class Private2 : Private1
    { }

    private class Private1
    {
        public sealed class Nested
        {
            public void Test( Foo<T> foo )
            {
                foo.Method2( this ); //Yup
                var nes = (Private2.Nested)this; //Yup
            }
        }
    }

    public void Method1()
    {
        var nested = new Private2.Nested();
        nested.Test( this );
    }

    private void Method2( Private2.Nested nested )
    {
        // something code...
    }
}