Struct Either with renaming in C#

EitherOr.cs

using System;
public class C {
    public Result<int>.Or M() =>
        Result<int>.Left(2);
}

public class Result<T> : Either<T, Exception> {}

public class Either<L, R> 
{
    // todo: + implicit ops to Or
    public static Or Left(L l) => new Or(l);
    public static Or Right(R r) => new Or(r);
    public struct Or 
    {
        L _l; R _r; byte _state;
        public bool IsLeft => _state == 0
            ? throw new InvalidOperationException("Not initialized " + GetType())
            : _state == 1;
        public Or(L l) { _l = l; _r = default; _state = 1; }
        public Or(R r) { _l = default; _r = r; _state = 2; }
        public T Match<T>(Func<L,T> left, Func<R,T> right) =>
            IsLeft ? left(_l) : right(_r);
    }
}