带有嵌套 Order By 的 Linq 查询？

Question

Hi there I have the following class structure:

class Apple
{
    public IEnumerable<Banana> Bananas { get; set; }
}

class Banana
{
    public IEnumerable<Carrot> Carrots { get; set; }
}

class Carrot
{
    public DateTime DateCreated { get; set; }
    public IEnumerable<Dog> Dogs { get; set; }
}

class Dog
{
    public string Target { get; set; }
}

I am trying to query all from a collection of Type Apple where Apples.Bananas.Carrots.Dogs.Target matches my input. I currently have.

var result = Apples.Where(apple => 
            apple.Bananas.Any(banana => 
                banana.Carrots.Any(carrort => carrort.Dogs.Any(dog => 
                    dog.Target.Equals(input)))));

My difficulty is I now realize I only want the newest entry from the Carrots list.

I have not been able to figure out how to order the carrots by DateCreated descending and take first within this query.

I have tried the following but its throwing and exception:

var result = Apples.Where(apple =>
    apple.Bananas.Any(banana =>
        banana.Carrots.OrderByDescending(carrot =>
            carrot.DateCreated).First().Dogs.Any(dog =>
                dog.Target.Equals(input))));

Exception Exception of type 'Antlr.Runtime.NoViableAltException

Answer 1

If you're ever unsure about your LINQ query, by all means, you should simplify it. Remember, LINQ will continue to return IEnumerable until you ask for an object (First, ToArray, ToList, etc.). Therefore, there's no harm in simplifying the code in the name of simplicity and debugging.

var ohGodMyEyes = Apples
   .Where(apple => apple.Bananas
       .Any(banana => banana.Carrots
           .OrderByDescending(carrot => carrot.DateCreated)));

var result = ohGodMyEyes
    .First().Dogs
    .Any(dog => dog.Target.Equals(input));