[RESOLVED] [2005] Variable 'myStreamReader' is used before it has been assigned a value

[jeffnyc]

I am receiving the following warning:

Warning 1 Variable 'myStreamReader' is used before it has been assigned a value. A null reference exception could result at runtime.

Here's my code:

Public Sub loadData()
        'this reads the textfile and loads the checkbox
        Dim currentFields() As String
        ' The StreamReader must be defined outside of the Try-Catch block
        '   in order to reference it in the Finally block.

        Dim myStreamReader As StreamReader
        Dim myInputString As String
        Dim rowCount As Integer = 0

        ' Ensure that the creation of the new StreamReader is wrapped in a 
        '   Try-Catch block, since an invalid filename could have been used.
        Try
            ' Create a StreamReader using a Shared (static) File class.
            myStreamReader = File.OpenText(filePath)
            ' Begin by reading a single line
            myInputString = myStreamReader.ReadLine()
            ' Continue reading while there are still lines to be read
            While Not myInputString Is Nothing
                currentFields = Split(myInputString, ",")
                If currentFields(1) = "0" Then
                    lstApts.Items.Add(currentFields(0))
                Else
                    lstApts.Items.Add(currentFields(0), True)
                End If
                rowCount += 1
                ' Read the next line.
                myInputString = myStreamReader.ReadLine()
            End While
        Catch exc As Exception
            ' Show the error to the user.
            MsgBox("File could not be opened or read." + vbCrLf + _
                "Please verify that the filename is correct, " + _
                "and that you have read permissions for the desired " + _
                "directory." + vbCrLf + vbCrLf + "Exception: " + exc.Message)
        Finally
            ' Close the object if it has been created.
            If Not myStreamReader Is Nothing Then
                myStreamReader.Close()
            End If
        End Try
    End Sub

Warning caused on If statement of Finally block.

[SharkC382]

This is just a warning that mystreamreader MAY NOT be anything by the time it reaches the Finally block.
You have mystreamreader DIMed as a streamreader, but it doesnt mean anything until you assign it with the File.OpenText method. If that were to fail, then mystreamreader would still be uninitialized when it reaches the Finally block.

That's why there's a warning. It's okay.

[jmcilhinney]

You can get rid of that warning message by changing this:

Dim myStreamReader As StreamReader

to this:

Dim myStreamReader As StreamReader = Nothing

The IDE gives you the warning because it doesn't know whether you intended that variable to be Nothing or you simply forgot to assign a value to it. By explicitly setting the variable to Nothing you are telling the compiler that it is Nothing because you intended it to be Nothing and that you will take responsibility for making sure that it is not Nothing if and when it is accessed.