Get No-repeat Random Value

RandomMng.cs

public static class RandomMng
{
    private static Random random = new Random();
    
    public static int GetRandomInt32(ICollection<int> coll)
    {
        int ret;
        do
        {
            ret = random.Next();
        } while (coll.Contains(ret));
        return ret;
    }
    
    public static ulong GetRandomUInt64(ICollection<ulong> coll)
    {
        ulong ret;
        do
        {
            var num = new byte[8];
            random.NextBytes(num);
            ret = BitConverter.ToUInt64(num, 0);
        } while (coll.Contains(ret));
        return ret;
    }
}