Question

I have a imprmented sort method for a colection in my code and today i noticed something strange. When i tried to add new enum values to the enum the sort method crashed with this error.

Unable to sort because the IComparer.Compare() method returns inconsistent results. Either a value does not compare equal to itself, or one value repeatedly compared to another value yields different results. x: ”, x’s type: ‘Texture2D’, IComparer: ‘System.Array+FunctorComparer`1[Microsoft.Xna.Framework.Graphics.Texture2D]’.

This seems really strange seens the sort is in now way dependent on earlyer result and all it should do is sort after the index of the enum insteed of alfabatic order.

Here is the code.

    availableTiles.Sort(CompareTilesToEnum);

    private static int CompareTilesToEnum(Texture2D x, Texture2D y)
    {
        int xValue = (int) (Enum.Parse(typeof(TileTyp), x.Name, true));
        int yValue = (int) (Enum.Parse(typeof(TileTyp), y.Name, true));
        if (xValue > yValue)
        {
            return 1;
        }
        else
        {
            return -1;
        }
    }

    public enum TileTyp
    {
        Nothing = -1,
        Forest,
        Grass,
        GrassSandBottom,
        GrassSandLeft,
        GrassSandRight,
        GrassSandTop,
        Mounten,
        Sand,
        Snow,
        Water,
        GrassSandTopLeft,
        GrassSandAll,
        GrassSandBottomLeft,
        GrassSandBottomRightLeft,
        GrassSandBottomRightTop,
        GrassSandBottomTopLeft,
        GrassSandRightLeft,
        GrassSandRightTop,
        GrassSandRightTopLeft,
        GrassSandBottomRight,
        GrassSandBottomTop
    }

The values i added was

    GrassSandBottomRight,
    GrassSandBottomTop

Answer 1

Your comparison never returns 0 – even if the values are equal. Any reason you don’t just ask int.CompareTo to compare the values?

private static int CompareTilesToEnum(Texture2D x, Texture2D y)
{
    int xValue = (int) (Enum.Parse(typeof(TileTyp), x.Name, true));
    int yValue = (int) (Enum.Parse(typeof(TileTyp), y.Name, true));
    return xValue.CompareTo(yValue);
}

Simpler and more importantly, it should actually work 🙂