Handling missing dll exception

[kimiraikkonen]

Hi,
I have an mini application with a dll named classlibrary1.

I used it via imports statement, but i tried something to catch a
custom msgbox error if the dll is not found or bad for the user.

I tried catch blabla as dllnotfoundexception with no help. Also try-
catch couldn't handle missing dll exception.

Could you define a sample code which calls a simple msgbox when a
button is pressed (if dll is missing)?

thanks

[Phill W.]

kimiraikkonen wrote:

I have an mini application with a dll named classlibrary1.
I used it via imports statement,

.... (you referenced it first, but anyway) ...

but i tried something to catch a custom msgbox error if the dll
is not found or bad for the user.

Where are you trying to catch this error?

..Net code is loaded and linked method-by-method so, as soon as you try
to /call/ a method that uses your dll and it's not there, Boom! That
method fails to "appear", and you get a TypeLoadException (usually).

/If/ you can wrap a Try .. Catch around the call to /that/ routine, you
stand a chance:

Try
LoadCL1()
Catch ex As TypeLoadException
' Oops
End Try

Sub LoadCL1()

Dim olib as New classlibrary1()
. . .

End Sub

This /won't/ work ...

Sub LoadCL2()
Try
Dim olib as New classlibrary1()
. . .
Catch ex As TypeLoadException
' Oops
End Try
End Sub

.... because the /whole method/ gets loaded in one go and the referenced
libraries, etc. loaded. The code fails /before/ it even starts to
execute your "Try".
(BTW, this has caused me /great/ confusion in the past where the method
that's failing to load is the Elapsed event handler on a Timer!).

HTH,
Phill W.

[kimiraikkonen]

On Dec 6, 7:12 pm, "Phill W." <p-.-a-.-w-a-r...@-o-p-e-n-.-a-c-.-u-k>
wrote:

kimiraikkonen wrote:

I have an mini application with a dll named classlibrary1.
I used it via imports statement,

... (you referenced it first, but anyway) ...

but i tried something to catch a custom msgbox error if the dll
is not found or bad for the user.

Where are you trying to catch this error?

.Net code is loaded and linked method-by-method so, as soon as you try
to /call/ a method that uses your dll and it's not there, Boom! That
method fails to "appear", and you get a TypeLoadException (usually).

/If/ you can wrap a Try .. Catch around the call to /that/ routine, you
stand a chance:

Try
LoadCL1()
Catch ex As TypeLoadException
' Oops
End Try

Sub LoadCL1()

Dim olib as New classlibrary1()
. . .

End Sub

This /won't/ work ...

Sub LoadCL2()
Try
Dim olib as New classlibrary1()
. . .
Catch ex As TypeLoadException
' Oops
End Try
End Sub

... because the /whole method/ gets loaded in one go and the referenced
libraries, etc. loaded. The code fails /before/ it even starts to
execute your "Try".
(BTW, this has caused me /great/ confusion in the past where the method
that's failing to load is the Elapsed event handler on a Timer!).

HTH,
Phill W.

I used catch inside button1.click sub. No luck. Then i tried inside
try-catch inside class library (dll) no luck again. Then tried "catch
xx as dllnotfoundexception" inside button1.click sub with no luck.

Could you simplify and sample with a more understanding way?

Very thanks.