private static LambdaExpression GetSelectManyCollectionSelector(LambdaExpression groupJoinResultSelect)
{
ParameterExpression parameter = Expression.Parameter(groupJoinResultSelect.ReturnType);
MemberExpression innerSource = Expression.Property(parameter, parameter.Type.GetProperty(nameof(Tuple <Object, Object> .Item2)));
Type innerType = OeExpressionHelper.GetCollectionItemType(innerSource.Type);
MethodCallExpression defaultIfEmptyCall = Expression.Call(OeMethodInfoHelper.GetDefaultIfEmptyMethodInfo(innerType), innerSource);
return(Expression.Lambda(defaultIfEmptyCall, parameter));
}