C＃对象引用未设置为对象的实例（在堆栈跟踪中未提及空引用）

Question

在发布模式下运行Windows服务时，出现“对象引用未设置为对象实例”错误（请注意，正如您从堆栈跟踪中看到的那样，它没有提及与NullReference有关的任何内容让我更加困惑）。 每次我在调试模式下运行此代码时，代码都能正常工作，但是一旦我构建它以在服务器上发布并启动它，它就会因对象引用错误而失败。 请参阅下面的堆栈跟踪，然后在下面的代码跟踪。

=================================================================================

Error Message: [EventQueueBulkProcessingHandler] Failed to process events
Stack Trace: 

Error Message (INNER EXCEPTION LEVEL 1): Object reference not set to an instance of an object.
Stack Trace (INNER EXCEPTION LEVEL 1):
   at Voicebox.EventTriggers.Processing.Preparation.EventContactsFilter.Filter(ContactsModel contacts, ContactsFilterModel contactsFilterModel, Int32 clientId) in D:\Websites\VoiceboxTest\Voicebox\VoiceBox.EventTriggers\Processing\Preparation\EventContactsFilter.cs:line 24
   at Voicebox.EventTriggers.Processing.Preparation.TriggerActionDetailsBuilder.CreateTriggerActionDetails(Trigger trigger, ITriggerEvent triggerEvent) in D:\Websites\VoiceboxTest\Voicebox\VoiceBox.EventTriggers\Processing\Preparation\TriggerActionDetailsBuilder.cs:line 48
   at Voicebox.EventTriggers.Processing.Handlers.UserEventsHandler.<>c__DisplayClass6_0.<MapEventsToTriggers>b__0(Trigger t, ITriggerEvent e) in D:\Websites\VoiceboxTest\Voicebox\VoiceBox.EventTriggers\Processing\Handlers\UserEventsHandler.cs:line 62
   at Voicebox.EventTriggers.Helpers.PermutationsHelper.<>c__DisplayClass0_1`3.<Permutations>b__1(TB b) in D:\Websites\VoiceboxTest\Voicebox\VoiceBox.EventTriggers\Helpers\PermutationsHelper.cs:line 11
   at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
   at System.Linq.Enumerable.<SelectManyIterator>d__17`2.MoveNext()
   at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
   at System.Linq.Enumerable.<SelectManyIterator>d__17`2.MoveNext()
   at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at Voicebox.EventTriggers.Processing.Handlers.UserEventsHandler.<HandleAsync>d__5.MoveNext() in D:\Websites\VoiceboxTest\Voicebox\VoiceBox.EventTriggers\Processing\Handlers\UserEventsHandler.cs:line 37
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Voicebox.EventTriggers.Processing.EventQueueBulkProcessingHandler.<ProcessEventsGrouppedByClient>d__8.MoveNext() in D:\Websites\VoiceboxTest\Voicebox\VoiceBox.EventTriggers\Processing\EventQueueBulkProcessingHandler.cs:line 107
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Voicebox.EventTriggers.Processing.EventQueueBulkProcessingHandler.<ProcessInternal>d__6.MoveNext() in D:\Websites\VoiceboxTest\Voicebox\VoiceBox.EventTriggers\Processing\EventQueueBulkProcessingHandler.cs:line 52

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因此，从上面的堆栈跟踪中可以看出，问题出在第24行的EventContactsFilter文件中。这对我来说毫无意义，因为这是List的初始化。 见下面的代码；

            // this is the line 24 which the stack trace points too
            List<string> filterExpressions = new List<string>();

            foreach (var model in contactsFilterModel.Criteria)
            {
                string fieldName = GetFieldName(contacts.ListId, model.FieldID, clientId);

                FieldType fieldType = GetFieldType(model);
                FilterExpression FilterExpression = ExpressionBuilder.GetFilterExpression(fieldName, model, fieldType);
                var expression = FilterExpression.sqlExpression;
                filterExpressions.Add(expression);
            }

因此，正如您所看到的，创建新列表时会抛出该错误，并且经过许多小时或在网上搜索后，我仍无法找出可能导致此问题的原因。 如果有人能够提供帮助，我将永远在您的债务中！！

Answer 1

我不是很确定问题是List<string>声明。 请在该声明周围使用try-catch ，并查看实际的错误消息是什么。

我的直觉说问题不存在。 也许在那条线的上方或下方。 我的猜测是foreach 。 无论哪种方式，请try-catch该代码:)