提问人：zwheeler 提问时间：4/6/2023 最后编辑：John Alexiouzwheeler 更新时间：4/6/2023 访问量：58
字符串拆分函数的 System.NullreferenceException [duplicate]
System.NullreferenceException for String split function [duplicate]
问：
我是 C# 的新手，正在修改我的第一个大程序。我不断得到以下内容，我不确定如何更新它，您的帮助将不胜感激
baseErrorCodes = New List(Of String)()
Dim errorCodeDescription As String = String.Empty
Dim baseCode As String
For Each errorCode As String In errorCodes
Dim matchingBusinessRuleByResponseCode As BusinessRule = Me.DomainData.Common.BusinessRules _
.FirstOrDefault(Function(businessRule) (businessRule.ApplicationSource = Me.BusinessRuleSource _
OrElse businessRule.ApplicationSource = "Maryland") _
AndAlso businessRule.ResponseCode = errorCode)
baseCode = errorCode.Split("-")(0)
If (matchingBusinessRuleByResponseCode IsNot Nothing) Then
If (String.IsNullOrWhiteSpace(fieldSource)) Then
fieldSource = matchingBusinessRuleByResponseCode.FieldSource
End If
错误信息
答：
0赞
John Alexiou
4/6/2023
#1
所以是空的。这是未找到匹配项的结果，字符串类型的默认值为 null。这是 的预期行为。errorCode.FirstOrDefault()
要解决此问题，请在调用 之前添加检查。If errorCode IsNot null Then ....Split()
或用于处理。String.IsNullOrEmpty()
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