Error: System.ArgumentException

[Richard de Beer]

Hi,

I've got some old code(VB6) which has been upgraded to VB.net.
In the old code, the undocumented function "VarPtr" is used. But in VB.net,
this function is no longer supported. I've searched the internet and found
some code withch should solve the problem.

This is the code:

Public Function VarPtr(ByVal o As Object) As Integer
Dim GC As System.Runtime.InteropServices.GCHandle =
System.Runtime.InteropServices.GCHandle.Alloc(o,
System.Runtime.InteropServices.GCHandleType.Pinned )
Dim ret As Integer = GC.AddrOfPinnedObject.ToInt32
GC.Free()
Return ret
End Function

But this code generates an error:

"An unhandled exception of type 'System.ArgumentException' occurred in
mscorlib.dll Additional information: Object contains non-primitive or
non-blittable data."

Since I'm a beginner, I was hoping that you could help me with this problem.

Thanks a lot!

[Rob Richardson]

Richard,

VarPtr() is a very advanced piece of Visual Basic. It's not documented for
a reason (although I can't tell you what it is). The best I can think of
for you to do is to try to figure out what it's used for in the original
code and find some way to write new code that does the same thing.

Good luck!

Rob

[Armin Zingler]

"Richard de Beer" <richard at -geen zooi en spam enzo - moviat.nl>
schrieb

Public Function VarPtr(ByVal o As Object) As Integer
Dim GC As System.Runtime.InteropServices.GCHandle =
System.Runtime.InteropServices.GCHandle.Alloc(o,
System.Runtime.InteropServices.GCHandleType.Pinned )
Dim ret As Integer = GC.AddrOfPinnedObject.ToInt32
GC.Free()
Return ret
End Function

But this code generates an error:

"An unhandled exception of type 'System.ArgumentException' occurred
in mscorlib.dll Additional information: Object contains non-primitive
or non-blittable data."

Since I'm a beginner, I was hoping that you could help me with this
problem.

I think after calling GC.Free, the ret value gets invalid because the object
isn't pinned anymore. In addition, if the object is a value type, it
is destroyed when the functions returns
But, what are you trying to achieve?
--
Armin

http://www.plig.net/nnq/nquote.html
http://www.netmeister.org/news/learn2quote.html

[Herfried K. Wagner [MVP]]

* "Richard de Beer" <richard at -geen zooi en spam enzo - moviat.nl> scripsit:

I've got some old code(VB6) which has been upgraded to VB.net.
In the old code, the undocumented function "VarPtr" is used. But in VB.net,
this function is no longer supported. I've searched the internet and found
some code withch should solve the problem.
Try to find a way around using this function. Why do you need it? What
exactly do you want to do? Maybe there is a much cleaner and better
solution.
This is the code:

Public Function VarPtr(ByVal o As Object) As Integer
Dim GC As System.Runtime.InteropServices.GCHandle =
System.Runtime.InteropServices.GCHandle.Alloc(o,
System.Runtime.InteropServices.GCHandleType.Pinned )
Dim ret As Integer = GC.AddrOfPinnedObject.ToInt32
GC.Free()
Return ret
End Function
You must not free the 'GC' here, but that's not the main problem.
But this code generates an error:

"An unhandled exception of type 'System.ArgumentException' occurred in
mscorlib.dll Additional information: Object contains non-primitive or
non-blittable data."

Blittable and Non-Blittable Types
<http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconblittablenon-blittabletypes.asp>

--
Herfried K. Wagner [MVP]
<http://www.mvps.org/dotnet>