Randomize a List in C#

This post will discuss how to randomize a List in C#.

1. Using `Enumerable.OrderBy` Method

The Enumerable.OrderBy method sorts the elements of a sequence using the specified comparer. We can tweak it as follows to shuffle items in random order by using a random number generator. Note that this creates a shuffled copy of the source list and leaves the source list unchanged.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> values = new List<int>() { 1, 2, 3, 4, 5 };

Random rand = new Random();

var shuffled = values.OrderBy(_ => rand.Next()).ToList();

Console.WriteLine(String.Join(", ", shuffled));

}

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2. Using Loop

To in-place randomize a list, we can write an extension method based on the Fisher–Yates shuffle algorithm. This can be implemented as follows in C#.

using System;

using System.Linq;

using System.Collections.Generic;

public static class Extensions

{

private static Random rand = new Random();

public static void Shuffle<T>(this IList<T> values)

{

for (int i = values.Count - 1; i > 0; i--) {

int k = rand.Next(i + 1);

T value = values[k];

values[k] = values[i];

values[i] = value;

}

public class Example

{

public static void Main()

{

List<int> values = new List<int>() { 1, 2, 3, 4, 5 };

values.Shuffle();

Console.WriteLine(String.Join(", ", values));

}

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That’s all about randomizing a List in C#.

1. Using Enumerable.OrderBy Method

2. Using Loop

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1. Using `Enumerable.OrderBy` Method