Random.Next代码合同是否不正确？

public static int Next(int minValue, int maxValue)
{
    Random random = new Random();
    return random.Next(minValue, maxValue);
}

public sealed class RandomSingleton
{
    private static readonly RandomSingleton instance = new RandomSingleton();

    private Random random = new Random();

    private RandomSingleton()
    {
    }

    public static RandomSingleton Instance
    {
        get { return instance; }
    }

    public int Next(int minValue, int maxValue)
    {
        return random.Next(minValue, maxValue);
    }
}