我在自定义IComparer实现中收到一个空对象,尽管它正在应用的集合中没有空条目。我的理解是这可能是由IComparer实现中的不一致引起的。我无法在下面的代码中找到这可能发生的地方。
作为参考,目的是首先按“正确”属性对它们进行排序,然后如果它们相同,则根据“tiebreakerDelta”属性进行排序,该属性最接近零排序而不会过去。
public int Compare(IFoolsSortable a, IFoolsSortable b)
{
int value1 = a.correct;
int value2 = b.correct;
// compare the total correct first
if (value1 < value2) return 1;
if (value1 > value2) return -1;
// total correct is the same, sort on deltas (closest without going over)
value1 = a.tiebreakerDelta;
value2 = b.tiebreakerDelta;
// returning -1 says "put value1 higher in the list than value2"
// (higher means closer to the 0 element of the sorted array)
if (value1 == 0) return -1; // a zero is higher than anything!
if (value2 == 0) return 1; // ditto, for the other arg, if val1 isn't zero
if (value1 == value2) return 0; // after that, if they are the same, say so
// if both are negative, then the larger one goes higher
if (value1 < 0 && value2 < 0) return (value1 > value2) ? -1 : 1;
// if only one is negative, it goes higher
if (value1 < 0) return -1;
if (value2 < 0) return 1;
// finally, if both are postitive, lower one goes higher
return (value1 > value2) ? 1 : -1;
}
感谢您提供的任何帮助!
编辑:我确定这不是真正的空引用,它是由一些不一致引起的。此外,有时会显示此错误文本确认 -
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: 'ResultsLineViewModel',
不幸的是,断点并没有帮助我。
编辑:以下是ResultsLineViewModel实现IFoolsSortable接口的简短示例:
List<ResultsLineViewModel> ls = new List<ResultsLineViewModel>();
ResultsLineViewModel line1 = new ResultsLineViewModel();
line1.correct = 10;
line1.tiebreakerDelta = 0;
ls.Add(line1);
ResultsLineViewModel line2 = new ResultsLineViewModel();
line2.correct = 10;
line2.tiebreakerDelta = 2;
ls.Add(line2);
ResultsLineViewModel line3 = new ResultsLineViewModel();
line3.correct = 10;
line3.tiebreakerDelta = -3;
ls.Add(line3);
ResultsLineViewModel line4 = new ResultsLineViewModel();
line4.correct = 9;
line4.tiebreakerDelta = 0;
ls.Add(line4);
ls.Sort(new FoolsSort());
对此的正确排序是:Line1,line3,line2,line4
答案 0 :(得分:16)
如果a
大于b
,则Compare(a,b)
应返回1,Compare(b,a)
应返回-1。如果您有a.correct = b.correct
,a.tiebreakerDelta = 0
和b.tiebreakerDelta = 0
,那么这与Compare
方法不一致,因为您希望保留操作的顺序。
据我所见,你应该先做这个
if (value1 == value2) return 0; // after that, if they are the same, say so
然后这个:
if (value1 == 0) return -1; // a zero is higher than anything!
if (value2 == 0) return 1; // ditto, for the other arg, if val1 isn't zero
另请注意,您的逻辑是相反的,如果第一个比第二个更大,则应返回1,而不是-1。检查例如link