Sort a Dictionary by value in C#

原文地址：Sort a Dictionary by value in C#

This post will discuss how to sort a dictionary by value in C#.

1. Using OrderBy() Method

The idea is to sort the dictionary by value using the OrderBy() method. Then, you can collect each key-value pair in the sorted collection and create a new dictionary using the LINQ’s ToDictionary() method. Note that this works with .NET framework 3.5 and above and requires System.Linq namespace. The complete code is shown below:

 

 

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using System; using System.Linq; using System.Collections.Generic;   public class Example {     public static void Main()     {         Dictionary<string, int> dict = new Dictionary<string, int>() {             {"A", 15}, {"B", 10}, {"C", 12}, {"D", 20}, {"E", 14}         };           var sortedDict = dict.OrderBy(x => x.Value).ToDictionary(x => x.Key, x => x.Value);           Console.WriteLine(String.Join(", ", sortedDict));     } }

 

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Output:

[B, 10], [C, 12], [E, 14], [A, 15], [D, 20]

 
This works since a Dictionary<TKey,TValue> already implements IEnumerable. The following code uses LINQ query syntax to achieve the same without using the ToDictionary() method.

 

 

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using System; using System.Linq; using System.Collections.Generic;   public class Example {     public static void Main()     {         Dictionary<string, int> dict = new Dictionary<string, int>() {             {"A", 15}, {"B", 10}, {"C", 12}, {"D", 20}, {"E", 14}         };           var sortedDict = from item in dict orderby item.Value ascending select item;           Console.WriteLine(String.Join(", ", sortedDict));     } }

 

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Output:

[B, 10], [C, 12], [E, 14], [A, 15], [D, 20]

2. Using a List

Alternatively, you can save a sorted copy of the Dictionary as a List. The following code demonstrates this using the ToList() method.

 

 

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using System; using System.Linq; using System.Collections.Generic;   public class Example {     public static void Main()     {         Dictionary<string, int> dict = new Dictionary<string, int>() {             {"A", 15}, {"B", 10}, {"C", 12}, {"D", 20}, {"E", 14}         };           List<KeyValuePair<string, int>> mappings = dict.ToList();         mappings.Sort((x, y) => x.Value.CompareTo(y.Value));           Console.WriteLine(String.Join(", ", mappings));     } }

 

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Output:

[B, 10], [C, 12], [E, 14], [A, 15], [D, 20]

 
The above code can be shortened to below.

 

 

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using System; using System.Linq; using System.Collections.Generic;   public class Example {     public static void Main()     {         Dictionary<string, int> dict = new Dictionary<string, int>() {             {"A", 15}, {"B", 10}, {"C", 12}, {"D", 20}, {"E", 14}         };           List<KeyValuePair<string, int>> mappings = dict.OrderBy(d => d.Value).ToList();           Console.WriteLine(String.Join(", ", mappings));     } }

 

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Output:

[B, 10], [C, 12], [E, 14], [A, 15], [D, 20]

That’s all about sorting a dictionary by value in C#.