public EvaluatableQbservableProvider(IObservableEvaluator evaluator, Type sourceType)
{
Evaluator = evaluator ?? throw new ArgumentNullException(nameof(evaluator));
SourceType = sourceType;
}
internal EvaluatableQbservable(IObservableEvaluator evaluator)
{
Provider = new EvaluatableQbservableProvider(evaluator, GetType());
Expression = Expression.Constant(this);
}