Visual studio 2017 vs 2019 - SysatemNullReferenceException

Question

Hi

When i run my project in 2017, it works just fine but when i run it in 2019, i get a System.NullReferenceException. Here is my function

Public Function GetConnection() As SqlConnection
        Dim Connection As SqlConnection = Nothing
        Dim bNeedAdd As Boolean = False
        Try
            Connection = CType(_Connections(ConnString), SqlConnection)
        Catch ex As Exception
        End Try
        If Connection Is Nothing Then
            bNeedAdd = True
        End If
        If Connection Is Nothing OrElse Connection.State = ConnectionState.Broken OrElse Connection.State = ConnectionState.Closed Then
            Try
                Connection.Dispose() <--- Error line in 2019
                Connection = Nothing
            Catch ex As Exception
                Debug.Print("Connection already exists")
            End Try
            Connection = New SqlConnection
        End If

        'Always return an open connection
        If Connection.State = ConnectionState.Closed Then
            Connection.ConnectionString = ConnString
            ' Connection.Open()
        End If
        If bNeedAdd Then
            _Connections.Add(ConnString, Connection)
        End If
        Return Connection
    End Function

Seeing as this line is inside a Try Catch, I am wondering why its throwing this error. Is there a setting or a reason why this behaviour occurs?

Thanks

Answer 1

Hi,
if Connection Is Nothing you get NullReferenceException:

1. Set Connection to Nothing

    Dim Connection As SqlConnection = Nothing
    Dim bNeedAdd As Boolean = False
    Try
        Connection = CType(_Connections(ConnString), SqlConnection)
    Catch ex As Exception
   

2. Ignore Error if there isn't Connection in _Connections

    End Try
   
    If Connection Is Nothing Then
        bNeedAdd = True
    End If
   
    If `Connection Is Nothing` OrElse ... Then
        Try
            Connection.Dispose() <--- Error line in 2019
   

Change your code:

     If `Connection Is Nothing` OrElse ... Then
         Try
             Connection?.Dispose()

Answer 2

Thanks for the reply. The question mark (null Conditional Operator) makes all the difference :)