c# randomize List

Question

I know that a version of this question prob gets asked quite frequently, but i looked into the forums for the last days and tried to implement the Fisher-Yates shuffle, but i didn´t manage to do it since i always get an error since it doesn´t take Shuffle as a function and gives this error: Entscheidungsfragen.Shuffle(this System.Collections.Generic.IList)': Extension methods must be defined in a non-generic static class.

private static System.Random rng = new System.Random();  

public static void Shuffle<T>(this IList<T> list)  
{  
    int n = list.Count;  
    while (n > 1) {  
        n--;  
        int k = rng.Next(n + 1);  
        T value = list[k];  
        list[k] = list[n];  
        list[n] = value;  
    }  
}

private static void CreateList(string[] args)
{
    var scenes =new List<Action>(szene1, szene2);
    scenes.Shuffle ();
    foreach (Action sce in scenes)
        sce ();
}

I´d really appreciate if someone could help me, since i´m just lost cause i tried everything i found.

The class which contains the `Shuffle` extension method must be static and it must be accessible from `CreateList`. — Tim Schmelter, Jul 26 '17 at 13:30

score 3 · Accepted Answer · answered Jul 26 '17 at 13:31

The error says it. Move your extension method Shuffle into a non-generic static class like this:

public static class ListExtensions
{
    private static System.Random rng = new System.Random();

    public static void Shuffle<T>(this IList<T> list)  
    {  
        int n = list.Count;  
        while (n > 1) {  
            n--;  
            int k = rng.Next(n + 1);  
            T value = list[k];  
            list[k] = list[n];  
            list[n] = value;  
        }  
    }
}

thank you so much, i feel so dumb right now spending so much time on figuring it out :D — Boernie, Jul 26 '17 at 13:45

score 0 · Answer 2 · answered Jul 26 '17 at 13:32

Here is an extension class

public static class ExtensionClass
{
    private static System.Random rng = new System.Random();

    public static void Shuffle<T>(this IList<T> list)
    {
        int n = list.Count;
        while (n > 1)
        {
            n--;
            int k = rng.Next(n + 1);
            T value = list[k];
            list[k] = list[n];
            list[n] = value;
        }
    }
}

c# randomize List

2 Answers2