Generate random enum in C# 2.0.

Question

Could someone please point me toward a cleaner method to generate a random enum member. This works but seems ugly.

Thanks!

public T RandomEnum<T>()
{
  string[] items = Enum.GetNames(typeof( T ));
  Random r = new Random();
  string e = items[r.Next(0, items.Length - 1)];
  return (T)Enum.Parse(typeof (T), e, true);
}

Answer 1

public T RandomEnum<T>()
{ 
  T[] values = (T[]) Enum.GetValues(typeof(T));
  return values[new Random().Next(0,values.Length)];
}

_{Thanks to @[Marc Gravell] for ponting out that the max in Random.Next(min,max) is exclusive.}

Answer 2

Marxidad's answer is good (note you only need Next(0,values.Length), since the upper bound is exclusive) - but watch out for timing. If you do this in a tight loop, you will get lots of repeats. To make it more random, consider keeping the Random object in a field - i.e.

private Random rand = new Random();
public T RandomEnum<T>()
{ 
  T[] values = (T[]) Enum.GetValues(typeof(T));
  return values[rand.Next(0,values.Length)];
}

If it is a static field, you will need to synchronize access.

Answer 3

I'm not sure about c# but other languages allow gaps in enum values. To account for that:

enum A {b=0,c=2,d=3,e=42};

switch(rand.Next(0,4))
{
   case 0: return A.b;
   case 1: return A.c;
   case 2: return A.d;
   case 3: return A.e;
}

The major down side is keeping it up to date!

Not near as neat but more correct in that corner case.

---

As pointed out, the examples from above index into an array of valid values and this get it right. OTOH some languages (cough D cough) don't provide that array so the above is useful enough that I'll leave it anyway.

Answer 4

Silverlight does not have GetValues(), but you can use reflection to get a random enum instead.

private Random rnd = new Random();

public T RndEnum<T>()
{
    FieldInfo[] fields = typeof(T).GetFields(BindingFlags.Static | BindingFlags.Public);

    int index = rnd.Next(fields.Length);

    return (T) Enum.Parse(typeof(T), fields[index].Name, false);
}