Sort KeyValuePair List

A List contains many KeyValuePair struct instances. It can be sorted with the Sort List method. For advanced sorting, we need Comparison.

Comparison info

This code requires Comparison delegate implementations. We implement these as static int methods that call CompareTo.

Example code

Compare1 receives two KeyValuePair structs and returns the result of CompareTo on their Key. Compare2 returns the CompareTo of the Value.

using System;
using System.Collections.Generic;

class Program
{
    static int Compare1(KeyValuePair<string, int> a, KeyValuePair<string, int> b)
    {
        return a.Key.CompareTo(b.Key);
    }

    static int Compare2(KeyValuePair<string, int> a, KeyValuePair<string, int> b)
    {
        return a.Value.CompareTo(b.Value);
    }

    static void Main()
    {
        var list = new List<KeyValuePair<string, int>>();
        list.Add(new KeyValuePair<string, int>("Perl", 7));
        list.Add(new KeyValuePair<string, int>("Net", 9));
        list.Add(new KeyValuePair<string, int>("Dot", 8));

        // Use Compare1 as comparison delegate.
        list.Sort(Compare1);

        foreach (var pair in list)
        {
            Console.WriteLine(pair);
        }
        Console.WriteLine();

        // Use Compare2 as comparison delegate.
        list.Sort(Compare2);

        foreach (var pair in list)
        {
            Console.WriteLine(pair);
        }
    }
}
[Dot, 8]
[Net, 9]
[Perl, 7]

[Perl, 7]
[Dot, 8]
[Net, 9]

Program results

The List.Sort(Compare1) call sorts the List by the Key of the KeyValuePair. And the List.Sort(Compare2) call sorts the List by the Value int.

Compare1 -> Key
Compare2 -> Value

A summary

We sorted collections of KeyValuePairs. We can use other syntax forms and implementations, such as LINQ expressions or lambda expressions, to accomplish this task.