WEB API IQueryable skip() take()

Question

So i want to slice a "IQueryable" in C# ASP.NET Web Api but i can't make it work. With the code below it might get more clear what i want to do.

private TestTwoContext db = new TestTwoContext();


// GET: api/Fruits/thefruits
[HttpGet]
[Route("api/Fruits/thefruits")]
public IQueryable<Fruits> TheFruits()
{
    dynamic myList = db.Fruits;
    var FiveItems = Queryable.Take(Queryable.Skip(myList, 5), 5);
    return FiveItems;
}

this gives me error in browser console:

jquery-3.3.1.min.js:2 GET http://localhost:49771/api/Fruits/thefruits 500 (Internal Server Error)

i need to cut my list (db.Fruits) from the 5th element to the 10th element. Just like we slice arrays in JavaScript. Example:

var myList = array.slice(5, 10)

I have also tried this:

private TestTwoContext db = new TestTwoContext();


// GET: api/Fruits/thefruits
[HttpGet]
[Route("api/Fruits/thefruits")]
public IQueryable<Fruits> TheFruits()
{
    var myList = db.Fruits;
    var FiveItems = myList.Skip(5).Take(4);
    return FiveItems;
}

this gives me error in browser console: jquery-3.3.1.min.js:2 GET http://localhost:49771/api/Fruits/thefruits 500 (Internal Server Error)

the number in skip and take will be passed as parametars but that is not that part i am worried about... those number are just example for now. Any help would be appreciated.

This Conroler works without problems:

// GET: api/Fruits
public IQueryable<Fruits> GetFruits()
{
    return db.Fruits;
}

returns the whole list of fruits, which later i write it down in table in HTML.

This also works :

[HttpGet]
[Route("api/Fruits/thefruits")]
public IQueryable<Fruits> TheFruits()
{
    var myList = db.Fruits;
    var FiveItems = myList.Take(5);
    return FiveItems;
}

but it gives me the the first 5 elements... not from the 5th to 10th element.

Answer 1

Try updating your "TheFruits" method to the following:

// GET: api/Fruits/thefruits
[HttpGet]
[Route("api/Fruits/thefruits")]
public IQueryable<Fruits> TheFruits()
{
    dynamic myList = db.Fruits;
    var FiveItems = myList.Skip(5).Take(5);
    return FiveItems;
}

Sample Console app:

    using System.Linq;

    static void Main(string[] args)
    {
        int[] test = new[] { 1, 2, 3, 4, 5, 6, 7, 8 };

        var t = test.AsQueryable().Skip(5).Take(5);

        foreach (int i in t)
        {
            Console.WriteLine(i.ToString());
        }

        Console.ReadLine();
    }

Answer 2

This is what i had to do to make it work:

    [HttpGet]
    [Route("api/Fruits/thefruits")]
     public List<Fruits> TheFruits()
    {

        var myList = db.Fruits;
        var FiveItems = myList.AsEnumerable().Skip(5).Take(5).ToList();
        return FiveItems;

    }

Answer 3

Try this to understand Skip() and Take().

var list = new List<long>{0,1,2,3,4,5,6,7,8,9};
var secondList = list.AsQueryable().Skip(5).Take(5).ToList();
secondList

Skip(X) -> It ignores the first X items on the Iqueryable

Take(Y) -> Limits the max resultant results.

OUTPUT IS:

List<long>(5) { 5, 6, 7, 8, 9 }

Answer 4

It would be nice if you posted the 500 error but as a guess, it's probably because cannot Skip without calling an order by in EntityFramework

[HttpGet]
[Route("api/Fruits/thefruits")]
public IQueryable<Fruits> TheFruits()
{
    return db.Fruits.OrderBy(x => x.Id).Skip(4).Take(5);
}