Error: object reference not set to an instance of an object in VB.NET
If you see this error, is because you forgot to use the NEW function and/or your object is set to nothing.
It happens a lot when you do some coding and you haven’t tested it a lot.
Or if your code builds some XML nodes or elements, sometimes, you forgot to think at 1 or 2 situations.
If you are starting to have a lot of these errors, maybe because you are mixing basic value type and object.
A String or an integer is to simple stuff and you may not have the famous error message: object reference not set to an instance of an object.
If you dealing with something more complex (System.object, Autodesk.MidDocument, SeeExpert.Application, Office.Document….) , then the message will comes if you don’t create it correctly before using it.
Public Sub myFunction() Dim oForm_to_crash As Form oForm_to_crash.Show() End Sub |
Do something like this next time. (See Example):
Public Sub myFunction() Dim oForm_to_crash As Form oForm_to_crash = New Form ' Good : place the new here oForm_to_crash.Show() End Sub |
Avoid this: (because you won’t be able to surround the error correctly with the try-catch-finally):
Public Sub myFunction() Dim oForm_to_crash As New Form 'don't put the new here oForm_to_crash.Show() End Sub |
Always try to use the try-catch in your code:
Public Sub myFunction() Dim oForm_to_crash As Form 'don't put the new here Try oForm_to_crash = New Form oForm_to_crash.Show() Catch ex As Exception 'something here Finally 'something else here End Try End Sub |
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