Sort KeyValuePair List
This page was last reviewed on Dec 7, 2022.
Dot Net Perls
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.
Detail A new List of KeyValuePair instances is created. Three KeyValuePairs are created and added to the List.
Next The List is sorted with Compare1. The method target Compare1 is accepted as a Comparison delegate.
Then After printing the List, we sort it again with Compare2, and finally display the List again.
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.
Sort List, Lambda
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.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
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