public IEnumerable<Postion> Sourround(RasterPositionValue[,] cost,
Postion postion)
{
if (VisistedValid(cost, postion.LeftTop()))
yield return postion.LeftTop();
if (VisistedValid(cost, postion.Top()))
yield return postion.Top();
if (VisistedValid(cost, postion.RightTop()))
yield return postion.RightTop();
if (VisistedValid(cost, postion.Right()))
yield return postion.Right();
if (VisistedValid(cost, postion.RightButtom()))
yield return postion.RightButtom();
if (VisistedValid(cost, postion.Buttom()))
yield return postion.Buttom();
if (VisistedValid(cost, postion.LeftButtom()))
yield return postion.LeftButtom();
if (VisistedValid(cost, postion.Left()))
yield return postion.Left();
}
