• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 1701
  • Last Modified:

Why do I get "A first chance exception of type 'System.ArgumentException' occurred in mscorlib.dll" exception

Hi guy,
I'm a bit puzzled as to why I'm getting a "A first chance exception ..." when trying to remove an event handler using "RemoveHandler". I this particular case I have five (5) RemoveHandler statments looking identical, but with different parameters, and only the last statement fails.

The app appears to be working fine so I'm just a bit confused.

Any thoughts?

/Michael
0
gem56
Asked:
gem56
  • 3
  • 3
1 Solution
 
Bob LearnedCommented:
There are too many possibilities to be sure of anything, without more detail.
0
 
gem56Author Commented:
As part of creating a Form instance I added several event handlers that includes the following statement:
   "AddHandler Me.ParentSection.Panel.Click, AddressOf Me.Sections.ParentForm.DeselectAllSectionsClick"

Then as part of closing that Form I am removing the added event handlers amongst which is the following statement that compliments the AddHandler statement above:
   "RemoveHandler Me.ParentSection.Panel.Click, AddressOf Me.Sections.ParentForm.DeselectAllSectionsClick"

So I wasn't expecting any exceptions because stepping through the code I can't see any empty pointers, etc. so I'm a bit confused.

/Michael
0
 
Bob LearnedCommented:
Michael,

Do you have the full stack trace text for the exception?  When the form is closed, is it disposed?
0
Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

 
gem56Author Commented:
Sorry, I forgot to say that I get that message only in the IDE Immediate Window and not as a crash.
The Form also closes OK and all looks normal, except for those messages so I was just curious as to whether I should worry about that or not.

/Michael


0
 
Bob LearnedCommented:
I would ignore that exception with a Try/Catch block.
0
 
gem56Author Commented:
Actually I am using Try/Catch but (stupid me) I forgot to print the ex.Message from the "Catch ex As Exception", I only looked at the output in Immediate Window.

The message in (Catch ex As Exception) has the following message:
"Delegate to an instance method cannot have null 'This'."

That makes sense so, even though I expected all references to be valid, sometimes "Me.Sections.ParentForm' is Nothing and hence the failure.

Thanks for your assistance (as always).

/Michael
0

Featured Post

Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

  • 3
  • 3
Tackle projects and never again get stuck behind a technical roadblock.
Join Now