Object reference not set to an instance of the object.

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Hello! I have code:

VB

Public ImageList As ArrayList
    Dim strFileSize As String = ""
    Dim path As String = "c:\catalog_images\"
    Dim di As New IO.DirectoryInfo(Path)
    Dim aryFi As IO.FileInfo() = di.GetFiles("*.png")
    Dim fi As IO.FileInfo
    Dim counter As Integer = 1

And in constructor Sub New have:

VB

ImageList = Nothing
       For Each Me.fi In aryFi
           ImageList.Add(fi.FullName)
       Next

But calls error "Object reference not set to an instance of the object."
What is wrong?

Posted 8-Mar-13 13:48pm

Junoli

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[no name] 8-Mar-13 20:38pm

You set ImageList = Nothing and then tried to use it.

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-03-08T14:08:00

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown.

Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: wither make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.

Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object"[^].

[EDIT]

After you comment I can see one you bug: you assign the reference ImageList to Nothing (which is Null, in VB.NET), and later attempt to dereference it by calling ImageList.Add. That's it.

(I hope it's just a typo; doing it intentionally would mean having no clue in programming in general.)

(which shows that you don't have a clue on what you are doing; so nothing can help you, unless you sit down to learn some basics of prog

Good luck,

—SA