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
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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

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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.

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