System.NullreferenceException for String split function

Question

I am new to C# and modifying my first big program. I keep getting the following and and I am unsure how to New it up your help would be greatly appreciated

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

Error Message

The fact that this isn't C# may be a part of your confusion? — David, Apr 05 '23 at 21:27

score 0 · Answer 1 · answered Apr 05 '23 at 21:28

So errorCode is null. This is the result of not finding a match and the default for string type is null. This is the expected behavior of .FirstOrDefault().

To fix, add a check If errorCode IsNot null Then ... before calling .Split().

or use String.IsNullOrEmpty() to handle.

System.NullreferenceException for String split function

1 Answers1