How to sort array of objects by fields without linq and other classes? (in C#)

Question

Here is example of how to sort array of objects by it's fields. I need to create function which will do same thing but WITHOUT Linq, Generics or any other classes.

p.s You can add methods in Test class to compare fields.

using System;
using System.Linq;

class Test {
    public int Count;
    public int Sum;
}

class Program {
    static void Main() {
        Test a1 = new Test() {
            Count = 1 ,
            Sum = 20
        };
        Test a2 = new Test() {
            Count = 2 ,
            Sum = 10
        };
        Test a3 = new Test() {
            Count = 3 ,
            Sum = 30
        };

        var arr = new Test[] { a1, a2, a3};

        var result = arr.OrderBy(n => n.Count).ToList();

        foreach (var item in result) {
            Console.WriteLine(item.Count);
        }
    }

    static void MyOrder() {
        //function which will sort passed array of objects by fields
    }
}

I didn't downvote but I think the reason is that you have not demonstrated any code that you have even attempted. This is not a code writing service. — JohanP
– JohanP, Commented Aug 1, 2018 at 5:06
Possible duplicate of How to sort array of FileInfo objects in descending order without LINQ — Richardissimo
– Richardissimo, Commented Aug 1, 2018 at 5:17
Perhaps take a look at en.wikipedia.org/wiki/Sorting_algorithm. That should be a very good place to start. — Enigmativity
– Enigmativity, Commented Aug 1, 2018 at 7:06

Michał Turczyn · Accepted Answer · 2018-08-01 06:36:44Z

0

One method is to use Array.Sort() static method. But if you want to use it, you class must implement IComparable interface, for example:

class Test : IComparable
{
  public int Count;
  public int Sum;

  public int CompareTo(object obj)
  {
    if (!(obj is Test))
      throw new ArgumentException("You can't compare two objects of different types!");

    var test = (Test)obj;
    if (test.Count < this.Count) return 1;
    else if (test.Count > this.Count) return -1;
    else return 0;
  }
}

And then code would become:

var arr = new Test[] { a1, a3, a2 };
Array.Sort(arr);

EDIT:

If you want to change ordering field at runtime, you can use IComparer interface as folloing:

public class Test
{
  public int Count;
  public int Sum;
}

public class TestComparerBySum : IComparer<Test>
{
  public int Compare(Test x, Test y)
  {
    if (x.Sum > y.Sum) return 1;
    else if (x.Sum < y.Sum) return -1;
    else return 0;
  }
}

public class TestComparerByCount : IComparer<Test>
{
  public int Compare(Test x, Test y)
  {
    if (x.Count > y.Count) return 1;
    else if (x.Count < y.Count) return -1;
    else return 0;
  }
}

And use it in code like this:

var arr = new Test[] { a3, a2, a1 };

Array.Sort(arr, new TestComparerBySum());

Array.Sort(arr, new TestComparerByCount());

edited Aug 1, 2018 at 6:36

answered Aug 1, 2018 at 5:32

Michał Turczyn

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8 Comments

Luka Mamulaishvili Over a year ago

What if i want to sort by Count ? or i need to use both of them?

Michał Turczyn Over a year ago

@LukaMamulaishvili It compares by Count, take a look at CompareTo method! And try it, then you'll see that it compares just like you want.

Luka Mamulaishvili Over a year ago

sorry i mean sum. can i use both of them ?

Michał Turczyn Over a year ago

@LukaMamulaishvili If you want to use Sum, then change all Count to Sum in CompareTo method. What do you mean by "can i use both of them?" ??

Michał Turczyn Over a year ago

@LukaMamulaishvili Yes, your requirement was to not pass ordering field explicitly, so somehow you need to let the compiler know, what to compare by! And the only way is to write a code. So, yes, you need to change code everytime you change your mind, there's no way around.

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