List.Sort 异常 - 无法排序，因为 IComparer.Compare() 方法返回不一致的结果

Question

尝试执行列表排序时，出现以下错误：

无法排序，因为 IComparer.Compare() 方法返回的结果不一致。某个值与其自身比较不相等，或者一个值与另一个值重复比较会产生不同的结果。

请提出此问题背后可能的原因。

堆栈跟踪：

消息：无法排序，因为 IComparer.Compare() 方法返回不一致的结果。某个值与其自身比较不相等，或者一个值与另一个值重复比较会产生不同的结果。 IComparer：“Premise.PremiseLIVE.CommGateway.Workflows.Sequential.SequentialWorkflowData.TransportJobPriorityDataSort”。 StackTrace：位于 System.Collections.Generic.IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer（对象比较器） 在 System.Collections.Generic.ArraySortHelper

1.Sort(T[] keys, Int32 index, Int32 length, IComparer

1 比较器） 在 System.Array.Sort[T](T[] 数组，Int32 索引，Int32 长度，IComparer

1 comparer) at System.Collections.Generic.List

1.Sort(Int32 索引，Int32 计数，IComparer`1 比较器) 在 Premise.PremiseLIVE.CommGateway.Workflows.Sequential.WorkflowActivities.wcSortTransportJobs.ExecuteSequential(ActivityExecutionContextexecutionContext) 来源：mscorlib TargetSite：无效 ThrowOrIgnoreBadComparer（System.Object）”

代码：

    IComparer<JobPriorityData> comparer = null;
                        comparer = new TransportJobPriorityDataSort( orgTransportTyps, transportPriorities, false );

                        if ( comparer != null )
                        {
                            jobList.Sort( comparer );
                        }

---

public TransportJobPriorityDataSort( OrgTransportTypCollection orgTransportTyps, TransportPriorityCollection transportPriorities, bool ascending )
    {
        _orgTransportTyps = orgTransportTyps;
        _transportPriorities = transportPriorities;

        _ascending = ascending;
        if ( !_ascending )
        {
            _xLTy = 1;
            _xGTy = -1;
        }

        _currentTime = DatabaseTimeHelper.DatabaseUtcTime;
    }

public int Compare( JobPriorityData x, JobPriorityData y )
    {
        try
        {
            // past-due jobs prioritized over not-past-due.
            if ( ( x.TransportPickupTime.Value <= _currentTime ) && ( y.TransportPickupTime.Value > _currentTime ) )
            {
                return ( _xGTy );
            }
            if ( ( x.TransportPickupTime.Value > _currentTime ) && ( y.TransportPickupTime.Value <= _currentTime ) )
            {
                return ( _xLTy );
            }

            // either: (A) both jobs are past-due or (B) neither job is past-due.

            // Order by Typ
            if ( _orgTransportTyps[ x.JobTransportType ].AssignSeqNbr > _orgTransportTyps[ y.JobTransportType ].AssignSeqNbr )
            {
                return ( _xLTy );
            }
            if ( _orgTransportTyps[ x.JobTransportType ].AssignSeqNbr < _orgTransportTyps[ y.JobTransportType ].AssignSeqNbr )
            {
                return ( _xGTy );
            }

            // then by pickup time
            if ( x.TransportPickupTime < y.TransportPickupTime )
            {
                return ( _xGTy );
            }
            if ( x.TransportPickupTime < y.TransportPickupTime )
            {
                return ( _xLTy );
            }
        }
        catch ( Exception )
        {
        }

        return ( _xEQy );

    }