Null reference exception warning

Posted on 2007-03-30
Last Modified: 2013-11-26
I have following code in VB.NEt 2005:

Dim objCardDetails As frmtCardDetails

        'I have some 20 lines of code here and then the below code
                intAccountNr = GetAccountNr()
            objCardDetails = New frmtCardDetails(intAccountNr )
End Try

Now I get following warning:
Warning      9      Variable 'objCardDetails' is used before it has been assigned a value. A null reference exception could result at runtime.

How should I initialize this variable?

Question by:vj_mi
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
  • 2
LVL 143

Accepted Solution

Guy Hengel [angelIII / a3] earned 250 total points
ID: 18824664
do you use the variable objCardDetails somewhere above that line? I guess so, because otherwise that warning should not be issued
LVL 86

Expert Comment

by:Mike Tomlinson
ID: 18824735
I agree.

Show us the 20 lines:

    "I have some 20 lines of code here and then the below code"

or more of your code...

Author Comment

ID: 18824787
No I have not used that variable. I have similar issue at most of the places. I declare a variable of type form and I use it somewhere down belowI get this error.

The earlier code is somthing like this:
        If c.Style Is Nothing Then
            If mViewStyle Is Nothing Then
                mViewStyle = grdTemp.Styles.Add(c.FieldName, "")
                mViewStyle.Options = StyleOptions.UseHorzAlignment
            End If
            c.StyleName = mViewStyle.StyleName
        End If
        c.Style.HAlignment = HorzAlignment.Near

How Do You Stack Up Against Your Peers?

With today’s modern enterprise so dependent on digital infrastructures, the impact of major incidents has increased dramatically. Grab the report now to gain insight into how your organization ranks against your peers and learn best-in-class strategies to resolve incidents.

LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 18824925
do you have that line:
objCardDetails = New frmtCardDetails(intAccountNr )
inside an if / else statement?


Author Comment

ID: 18828924
No... it is not inside the If statement.

What will happen if I initialize to Nothing, like:

Dim objCardDetails As frmtCardDetails = nothing

LVL 86

Assisted Solution

by:Mike Tomlinson
Mike Tomlinson earned 250 total points
ID: 18829153
It can't hurt.

...but still shouldn't make a difference given the code you've posted thus far.

Featured Post

Guide to Performance: Optimization & Monitoring

Nowadays, monitoring is a mixture of tools, systems, and codes—making it a very complex process. And with this complexity, comes variables for failure. Get DZone’s new Guide to Performance to learn how to proactively find these variables and solve them before a disruption occurs.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Welcome my friends to the second instalment and follow-up to our Minify and Concatenate Your Scripts and Stylesheets (…
This article shows how to deploy dynamic backgrounds to computers depending on the aspect ratio of display
I've attached the XLSM Excel spreadsheet I used in the video and also text files containing the macros used below.…
Exchange organizations may use the Journaling Agent of the Transport Service to archive messages going through Exchange. However, if the Transport Service is integrated with some email content management application (such as an antispam), the admini…

726 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question