Sort an array of objects according to another array of objects in C# [duplicate]

Question

I have two objects. I want to sort first object's QuickLinks property according to second object's QuickLinks. It should be based on QuickLinkContent.ConfigId

NavigationMenuContent nmc1 = new NavigationMenuContent();
NavigationMenuContent nmc2 = new NavigationMenuContent();

public class NavigationMenuContent
    {
        public int LanguageID { get; set; }

        public QuickLinkContent[] QuickLinks { get; set; }
    }

public class QuickLinkContent
    {
        public Guid ConfigID { get; set; }

        public string Name { get; set; }

        public string Description { get; set; }

        public string Url { get; set; }

        public Guid? ServiceProviderID { get; set; }

        public SchemeContentFile Document { get; set; }
    }

I tried doing it like this:

nmc1.QuickLinks = nmc1.QuickLinks.OrderBy(q => nmc2.QuickLinks.ToList().IndexOf(q.ConfigID));

but getting error :

Cannot convert from System.Guid to QuickLnkContent.

You say you want to sort nmc1 list, but you are trying to sort QuickLinks array. So what you are actually trying to sort? — Sergey Berezovskiy
– Sergey Berezovskiy, Commented Jan 13, 2021 at 20:39
What does that even mean? For example, if I said "I want to sort this Person[] according to FirstName alphabetical descending" - that makes sense.. but "I want to sort this Person[] according to that Person[]" - it's not a specification of anything — Caius Jard
– Caius Jard, Commented Jan 13, 2021 at 20:40
@SergeyBerezovskiy sorry for confustion, I've updated the question — Prashant Yadav
– Prashant Yadav, Commented Jan 13, 2021 at 20:46

Enigmativity · Accepted Answer · 2021-01-13 21:13:22Z

3

I would use a dictionary to do this.

Dictionary<Guid, int> map =
    nmc2
        .QuickLinks
        .Select((x, n) => (x, n))
        .ToDictionary(z => z.x.ConfigID, z => z.n);

nmc1.QuickLinks =
    nmc1
        .QuickLinks
        .OrderBy(x => map[x.ConfigID])
        .ToArray();

answered Jan 13, 2021 at 21:13

Enigmativity

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1 Comment

Charlieface Over a year ago

This is the faster method usually

Sergey Berezovskiy · Accepted Answer · 2021-01-13 20:56:42Z

1

Create array of ordered config ids:

var orderedIds = nmc2.QuickLinks.Select(ql => ql.ConfigID).ToArray();

And then use it to order links

nmc1.QuickLinks = nmc1.QuickLinks
   .OrderBy(ql => Array.IndexOf(orderedIds, ql.ConfigID))
   .ToArray();

answered Jan 13, 2021 at 20:56

Sergey Berezovskiy

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2 Comments

Charlieface Over a year ago

O(n2) operation. The other solution will usually be faster

Sergey Berezovskiy Over a year ago

@Charlieface first of all it's premature optimization. You don't want to create dictionaries to sort an array of 5 items. And other solution will fail 1) when nmc1 has unique items, 2) when nmc2 has duplicates. So you (maybe) saved few ticks of cpu, but got more code to maintain and two problems to deal with

NetMage · Accepted Answer · 2021-01-13 21:44:28Z

1

Using an array extension method, you can solve this generally:

public static int IndexOfBy<T, TKey>(this T[] a, TKey target, Func<T,TKey> keyFn, EqualityComparer<TKey> cmp = null) {
    cmp = cmp ?? EqualityComparer<TKey>.Default;
    for (int j1 = 0; j1 < a.Length; ++j1) {
        if (cmp.Equals(keyFn(a[j1]), target))
            return j1;
    }
    return -1;
}

With the extension method available, you can use OrderBy:

nmc1.QuickLinks = nmc2.QuickLinks.OrderBy(q => nmc2.QuickLinks.IndexOfBy(q.ConfigID, q2 => q2.ConfigID)).ToArray();

answered Jan 13, 2021 at 21:44

NetMage

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