CODEWITHSUNDEEP
c#arrays
Gregion
Gregion

Reputation: 307

Array sorting by two parameters

I'm having a little difficulty with the array.sort. I have a class and this class has two fields, one is a random string the other one is a random number. If i want to sort it with one parameter it just works fine. But i would like to sort it with two parameters. The first one is the SUM of the numbers(from low to high), and THEN if these numbers are equal by the random string that is give to them(from low to high).

Can you give some hint and tips how may i can "merge" these two kinds of sort?

Array.Sort(Phonebook, delegate(PBook user1, PBook user2)
        { return user1.Sum().CompareTo(user2.Sum()); });
        Console.WriteLine("ORDER");

        foreach (PBook user in Phonebook)
        {
            Console.WriteLine(user.name);
        }

That's how i order it with one parameter.

Upvotes: 4

Views: 7123

Answers (3)

Rawling
Rawling

Reputation: 50104

You can do this in-place by using a custom IComparer<PBook>. The following should order your array as per your original code, but if two sums are equal it should fall back on the random string (which I've called RandomString):

public class PBookComparer : IComparer<PBook>
{
    public int Compare(PBook x, PBook y)
    {
        // Sort null items to the top; you can drop this
        // if you don't care about null items.
        if (x == null)
            return y == null ? 0 : -1;
        else if (y == null)
            return 1;

        // Comparison of sums.
        var sumCompare = x.Sum().CompareTo(y.Sum());
        if (sumCompare != 0)
            return sumCompare;

        // Sums are the same; return comparison of strings 
        return String.Compare(x.RandomString, y.RandomString);
    }
}

You call this as

Array.Sort(Phonebook, new PBookComparer());

You could just do this inline but it gets a bit hard to follow:

Array.Sort(Phonebook, (x, y) => { 
    int sc = x.Sum().CompareTo(y.Sum());
    return sc != 0 ? sc : string.Compare(x.RandomString, y.RandomString); });

... Actually, that isn't too bad, although I have dropped the null checks.

Upvotes: 1

Servy
Servy

Reputation: 203821

Here is the general algorithm that you'll use for comparing multiple fields in a CompareTo method:

public int compare(MyClass first, MyClass second)
{
    int firstComparison = first.FirstValue.CompareTo(second.SecondValue);

    if (firstComparison != 0)
    {
        return firstComparison;
    }
    else
    {
        return first.SecondValue.CompareTo(second.SecondValue);
    }
}

However, LINQ does make the syntax for doing this much easier, allowing you to only write:

Phonebook = Phonebook.OrderBy(book=> book.Sum())
            .ThenBy(book => book.OtherProperty)
            .ToArray();

Upvotes: 1

Behnam Esmaili
Behnam Esmaili

Reputation: 5967

i think this is what you are after:

sourcearray.OrderBy(a=> a.sum).ThenBy(a => a.random)

Upvotes: 12

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