How do I select a random value from an enumeration?

Question

Given an arbitrary enumeration in C#, how do I select a random value?

(I did not find this very basic question on SO. I\'ll post my answer in a minute as reference f

Answer 1

You could just do this:

var rnd = new Random();
return (MyEnum) rnd.Next(Enum.GetNames(typeof(MyEnum)).Length);

No need to store arrays

Answer 2

Use Enum.GetValues to retrieve an array of all values. Then select a random array item.

static Random _R = new Random ();
static T RandomEnumValue<T> ()
{
    var v = Enum.GetValues (typeof (T));
    return (T) v.GetValue (_R.Next(v.Length));
}

Test:

for (int i = 0; i < 10; i++) {
    var value = RandomEnumValue<System.DayOfWeek> ();
    Console.WriteLine (value.ToString ());
}

->

Tuesday
Saturday
Wednesday
Monday
Friday
Saturday
Saturday
Saturday
Friday
Wednesday

Answer 3

Call Enum.GetValues; this returns an array that represents all possible values for your enum. Pick a random item from this array. Cast that item back to the original enum type.

Answer 4

You can also cast a random value:

using System;

enum Test {
  Value1,
  Value2,
  Value3
}

class Program {
  public static void Main (string[] args) {
    var max = Enum.GetValues(typeof(Test)).Length;
    var value = (Test)new Random().Next(0, max - 1);
    Console.WriteLine(value);
  }
}

But you should use a better randomizer like the one in this library of mine.

Answer 5

Array values = Enum.GetValues(typeof(Bar));
Random random = new Random();
Bar randomBar = (Bar)values.GetValue(random.Next(values.Length));

Answer 6

Here is a generic function for it. Keep the RNG creation outside the high frequency code.

public static Random RNG = new Random();

public static T RandomEnum<T>()
{  
    Type type = typeof(T);
    Array values = Enum.GetValues(type);
    lock(RNG)
    {
        object value= values.GetValue(RNG.Next(values.Length));
        return (T)Convert.ChangeType(value, type);
    }
}

Usage example:

System.Windows.Forms.Keys randomKey = RandomEnum<System.Windows.Forms.Keys>();