Question

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

Asked by: running32

I have converted my program from 2003 to 2005 when I compile it I keep getting the error above. on many of my variables how can I fix this.  thanks

Warning      101      Variable 'byttreatment' is used before it has been assigned a value. A null reference exception could result at runtime.      C:\frmSCQustionnaire.vb      2284      2129      SqlParametersDB

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Asked On
2009-10-26 at 11:22:28ID24844559
Topic

Microsoft Visual Basic.Net

Participating Experts
5
Points
500
Comments
17

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Answers

 

by: Omego2KPosted on 2009-10-26 at 11:34:01ID: 25665258

The simplest solution would be to assign a value to it. If you would post your code and where the exception occurs it would help us help you with how you may proceed.

 

by: themrrobertPosted on 2009-10-26 at 11:35:11ID: 25665274

Make sure that all of your variables are initialized with values before you use them.

To be safe, initialize ALL variables with values as soon as you are about to use them.

Such as:

Dim A as String
A = "Test"

Dim i as integer
i  = 0
.....

Most likely you are just getting a nag message that won't actually cause an error, but for example, say you try to do this:

Dim myStr
MsgBox(myStr,0,"Title")

(Yes i know this is legacy code)

If myStr has no value, it could well have non-ascii or null characters within it, causing a corrupted messagebox at best, and an unhandled-exception leading to a crash or buffer-overflow at worst.

 

by: jpaulinoPosted on 2009-10-26 at 11:36:27ID: 25665297

You need to create a New instance of the class.

Ex.

Dim cls As New myClass

 

by: bhagwantsinghPosted on 2009-10-27 at 03:56:16ID: 25670889

Hi,

Which language are you using? In C# you must initialize variable before using it. If you are using VB then turn off option strict.

E.g.
Option Strict Off

 

by: CodeCruiserPosted on 2009-10-27 at 06:15:35ID: 25672015

>I keep getting the error above
>Warning      101      Variable 'byttreatment' is used before it has been assigned a value.

As you can see, the first word of the message is "Warning" which means that its not an error. It is just a precautionary warning to alert you so that you properly initialize variables to avoid runtime errors.

If the project is not compiling, goto Project Properties, Compile tab and see if the "Treat all warnings as errors" checkbox is ticked. Untick it.

 

by: Omego2KPosted on 2009-10-27 at 06:20:36ID: 25672065

haha good catch CodeCruiser.

 

by: jpaulinoPosted on 2009-10-27 at 07:46:47ID: 25672966

>> If the project is not compiling, goto Project Properties, Compile tab and see if the "Treat all warnings as errors" checkbox is ticked. Untick

Do you think that's a solution ? To skip future errors.

 

by: CodeCruiserPosted on 2009-10-27 at 07:50:16ID: 25673009

Off course its not. But in many cases, its simply not relevant. I get really annoyed when i declare a variable outside Try block and use it inside try block and VS keeps complaining that the local variable is not used etc. For objects, i think Not IsNothing check should be performed anyway.

 

by: jpaulinoPosted on 2009-10-27 at 07:57:40ID: 25673105

Try to use some class without create a new instance an look at the warning message.

Something like this:

Public Class Form1
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim cls As SomeClass
        cls.NewProperty = ""
    End Sub
 
End Class
 
Partial Class SomeClass
 
    Private newPropertyValue As String
    Public Property NewProperty() As String
        Get
            Return newPropertyValue
        End Get
        Set(ByVal value As String)
            newPropertyValue = value
        End Set
    End Property
 
End Class

                                              
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by: jpaulinoPosted on 2009-10-27 at 07:58:14ID: 25673115

You got:

Warning 1 Variable 'cls' is used before it has been assigned a value. A null reference exception could result at runtime. C:\Users\...\AppData\Local\Temporary Projects\WindowsApplication1\Form1.vb 5 9 WindowsApplication1

 

by: running32Posted on 2009-10-27 at 12:00:16ID: 31646043

thanks

 

by: jpaulinoPosted on 2009-10-27 at 12:06:49ID: 25676149

What was the solution for the problem ? Have you tried the way I have showed ?

 

by: jpaulinoPosted on 2009-11-03 at 13:32:53ID: 25734001

ModEErf,

The asker didn't made any comments so I recommend to leave this question as it is. She have choose a wrong answer and no respect to the other experts comments that tried to help and spent time with her showing some code and right solutions.

She have made is choice and I of course have to accept that.

 

by: Omego2KPosted on 2009-11-03 at 17:01:51ID: 25735546

I agree, looking at my "solution" it's not a solution at all. I won't mind having points transfered from me to a more proper answer.

 

by: jpaulinoPosted on 2009-11-04 at 00:01:16ID: 25737250

Omego2K,

Just to clarify, is not a question of points at all !!!

 

by: Omego2KPosted on 2009-11-04 at 06:04:50ID: 25739370

I understand, it's a question of the proper solution. I agree that people who are searching on the issue will be confused.

20120131-EE-VQP-002

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