C#•3y ago

❔ How do i sort a list of objects by multiple possible items

Hey, i'm trying to write a method to return a list of objects by letting the user choose which item of the object they want it sorted by, code follows

33 Replies

Ash_OP•3y ago

public static List<Artikel> Auftragsliste = new();

public static List<Artikel> Auftragsliste = new();

this is my list, the object follows

public string Gtin;
public string Artikelnummer;
public string Bezeichnung;
public string Warengruppe;
public double Preis;

public string Gtin;
public string Artikelnummer;
public string Bezeichnung;
public string Warengruppe;
public double Preis;

I want the user to be able to choose by which of these items they want the list sorted by, does someone know what i could do? also if there is any relevant code missing tell me and i'll try to upload it

sibber•3y ago

take a Func that gives an object and returns the thing to sort by

Ash_OP•3y ago

hm?

sibber•3y ago

btw this already exists in linq

plam•3y ago

Ash_OP•3y ago

what's it called? i haven't seen a method like this

sibber•3y ago

https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.orderby?view=net-7.0

Enumerable.OrderBy Method (System.Linq)

Sorts the elements of a sequence in ascending order.

Ash_OP•3y ago

that looks complicated... i'd love to be able to do something like GetList(List,1) and have it output sorted by the first item, here a string

Anu6is•3y ago

it's not complicated, just look at the example provided

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void OrderByEx1()
{
    Pet[] pets = { new Pet { Name="Barley", Age=8 },
                   new Pet { Name="Boots", Age=4 },
                   new Pet { Name="Whiskers", Age=1 } };

    IEnumerable<Pet> query = pets.OrderBy(pet => pet.Age); //this is the part you are interested in

    foreach (Pet pet in query)
    {
        Console.WriteLine("{0} - {1}", pet.Name, pet.Age);
    }
}

/*
 This code produces the following output:

 Whiskers - 1
 Boots - 4
 Barley - 8
*/

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void OrderByEx1()
{
    Pet[] pets = { new Pet { Name="Barley", Age=8 },
                   new Pet { Name="Boots", Age=4 },
                   new Pet { Name="Whiskers", Age=1 } };

    IEnumerable<Pet> query = pets.OrderBy(pet => pet.Age); //this is the part you are interested in

    foreach (Pet pet in query)
    {
        Console.WriteLine("{0} - {1}", pet.Name, pet.Age);
    }
}

/*
 This code produces the following output:

 Whiskers - 1
 Boots - 4
 Barley - 8
*/

Ash_OP•3y ago

i'm on that site, tho i still don't understand how i use that for a list instead of an Array

plam•3y ago

It doesn't actually have any difference whether it's an array or list

public class Foo
{
    public string Name { get; }
    public int Age { get; }

    public Foo(string name, int age)
    {
        Name = name;
        Age = age;
    }

    public override string ToString() => "[" + Name + ", " + Age + "]";
}

public static class Program
{
    public static void Main()
    {
        Foo[] foos =
        {
            new Foo("First", 27), new Foo("Third", 21),
            new Foo("Second", 24), new Foo("Fourth", 30)
        };

        Foo[] sorted = foos.OrderBy(foo => foo.Age).ToArray(); // any field instead of its Age

        foreach (var it in sorted) Console.WriteLine(it);
    }
}

*/
// Before:
[First, 27]
[Third, 21]
[Second, 24]
[Fourth, 30]

// After:
[Third, 21]
[Second, 24]
[First, 27]
[Fourth, 30]
*/

public class Foo
{
    public string Name { get; }
    public int Age { get; }

    public Foo(string name, int age)
    {
        Name = name;
        Age = age;
    }

    public override string ToString() => "[" + Name + ", " + Age + "]";
}

public static class Program
{
    public static void Main()
    {
        Foo[] foos =
        {
            new Foo("First", 27), new Foo("Third", 21),
            new Foo("Second", 24), new Foo("Fourth", 30)
        };

        Foo[] sorted = foos.OrderBy(foo => foo.Age).ToArray(); // any field instead of its Age

        foreach (var it in sorted) Console.WriteLine(it);
    }
}

*/
// Before:
[First, 27]
[Third, 21]
[Second, 24]
[Fourth, 30]

// After:
[Third, 21]
[Second, 24]
[First, 27]
[Fourth, 30]
*/

Ash_OP•3y ago

it still tells me that there is no Artikel.OrderBy with "Artikel" being the object within the list

Anu6is•3y ago

probably missing the using

plam•3y ago

You have to use the LINQ method on the list of your objects, not on a single one. additionally add the using, that's what Anubis said

Ash_OP•3y ago

no, i'm using linq for other stuff too that at least does not show a error, lemme try something

plam•3y ago

Show it 👀

Ash_OP•3y ago

doesn't give me the list, does it save it in that "query" variable?

public static void GetList(int sortby)
        {
            switch (sortby)
            {
                default:
                    Console.WriteLine("Bitte geben Sie eine gültige Kategorie von 1-5 an");
                    break;
                case 1:
                    IEnumerable<Artikel> dummy = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Gtin);
                    break;
                case 2:
                    IEnumerable<Artikel> dummy1 = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Artikelnummer);
                    break;
                case 3:
                    IEnumerable<Artikel> dummy2 = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Bezeichnung);
                    break;
                case 4:
                    IEnumerable<Artikel> dummy3 = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Warengruppe);
                    break;
                case 5:
                    IEnumerable<Artikel> dummy4 = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Preis);
                    break;
            }
            
        }

public static void GetList(int sortby)
        {
            switch (sortby)
            {
                default:
                    Console.WriteLine("Bitte geben Sie eine gültige Kategorie von 1-5 an");
                    break;
                case 1:
                    IEnumerable<Artikel> dummy = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Gtin);
                    break;
                case 2:
                    IEnumerable<Artikel> dummy1 = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Artikelnummer);
                    break;
                case 3:
                    IEnumerable<Artikel> dummy2 = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Bezeichnung);
                    break;
                case 4:
                    IEnumerable<Artikel> dummy3 = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Warengruppe);
                    break;
                case 5:
                    IEnumerable<Artikel> dummy4 = Artikelliste.Auftragsliste.OrderBy(artikel => artikel.Preis);
                    break;
            }
            
        }

this is the method at this point

plam•3y ago

So, what is wrong with it? You're sorting your list and introducing an IEnumerable for it which now contains this sorted list.

IEnumerable<Artikel> dummy = Auftragsliste.OrderBy(artikel => artikel.Gtin);

IEnumerable<Artikel> dummy = Auftragsliste.OrderBy(artikel => artikel.Gtin);

Ash_OP•3y ago

so all i'm missing is a little dummy.ToString() for that? override already written

plam•3y ago

I mean like.. ToString doesn't impact your result code that's just a way of writing it in console. Just foreach your IEnumerable and display it in any way you want:

Either its an:
(override of ToString() or Console.WriteLine("{0} - {1}", obj.Field, obj.Field);

Either its an:
(override of ToString() or Console.WriteLine("{0} - {1}", obj.Field, obj.Field);

Ash_OP•3y ago

nvm override not working for that, if i put that into a Console.WriteLine i get this

System.Linq.OrderedEnumerable`2[Warenspeichersystem.Artikel,System.String]

System.Linq.OrderedEnumerable`2[Warenspeichersystem.Artikel,System.String]

plam•3y ago

Send your foreach method please, I'll just show you how it is supposed to be working.

Ash_OP•3y ago

there is none

plam•3y ago

So, you got a sorted IEnumerable as a result of your method which has to be displayed properly?

Ash_OP•3y ago

i guess? as i said all this have to do is to display it into the console, i don't need it to be saved somewhere

plam•3y ago

You don't need to create an instance of IEnumerable then.

foreach (var it in Auftragsliste.OrderBy(artikel => artikel.FIELD)) {
  Console.WriteLine(it);
}

foreach (var it in Auftragsliste.OrderBy(artikel => artikel.FIELD)) {
  Console.WriteLine(it);
}

Ash_OP•3y ago

that five times in a switch case so each field has it own possibility?

plam•3y ago

basically just change the specific field and override ToString() method in your Artikel class it's not a great way of implementing it but you'll be able to rewrite it after

cap5lut•3y ago

that would work but u would have a ton of duplicate code, i would store the Artikelliste.Auftragsliste as IEnumerable<Artikel> before the switch, then in the case branches simply do dummy = dummy.OrderBy(...) and after the switch use a foreach loop to print the elements

plam•3y ago

ikr but let them get the idea of the linq method first

Ash_OP•3y ago

Thank you so much that worked

plam•3y ago

Make sure to check out more documentation on this method, specifically just to avoid the myriad of duplicate code. gl

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ How do i sort a list of objects by multiple possible items