ClickOnce application: test if program is being run off line

[robertb_NZ]

I have a ClickOnce application published with option "The application is available offline as well". When run from the web page it is passed a URI query, so I need to know if it is being run offline, or from Visual Studio. I have the following code, which works, but is there a better way that doesn't use Try/Catch, to avoid relying on error trapping for "normal logic".

If System.Diagnostics.Debugger.IsAttached Then ' Case 1: Debugging (run from Visual Studio)

' Set Debugging defaults​

Else

Try ' Case 2. Run from JazzSoftware web page.

QueryString = ApplicationDeployment.CurrentDeployment.ActivationUri.Query
HandleParameters() ' Parameter received with download
' Encrypt and save query string
​

Catch ex As Exception ' Case 3. Run downloaded copy offline

QueryString = Decrypt(saved query string)
HandleParameters()
​

End Try​

End If

Thank you, Robert.

 

[jmcilhinney]

What's the exception that gets thrown? I don't really use ClickOnce so I don't know the answer to your question off the top of my head but the nature of the exception may lead to an answer.

 

[robertb_NZ]

Thanks John, that was the right question. The answer: Unhandled exception, caused by "Object reference not set to an instance of an object".

Which got me thinking: the problem was clearly somewhere in the ApplicationDeployment.CurrentDeployment object. So I put in a diagnostic: -
If IsNothing(ApplicationDeployment.CurrentDeployment) Then

MsgBox("#1")​

ElseIf IsNothing(ApplicationDeployment.CurrentDeployment.ActivationUri) Then

MsgBox("#2")​

ElseIf IsNothing(ApplicationDeployment.CurrentDeployment.ActivationUri.Query) Then

MsgBox("#3")​

End If

The test => "#2".

So I was able to fix the problem like this: -
If System.Diagnostics.Debugger.IsAttached Then ' Case 1: Debugging (run from Visual Studio)

' Code for debugging​

ElseIf IsNothing(ApplicationDeployment.CurrentDeployment) OrElse IsNothing(ApplicationDeployment.CurrentDeployment.ActivationUri) _

OrElse IsNothing(ApplicationDeployment.CurrentDeployment.ActivationUri.Query) Then​

' Case 3. Run downloaded copy offline. This is the code that was previously in the Catch​

Else

' Case 2. Run from JazzSoftware web page.​

End If

I really only need the 2nd condition in

ElseIf IsNothing(...) OrElse IsNothing(...) OrElse IsNothing(...) Then​

However I thought that it would be safer to check each level of the hierarchy in case I don't understand enough about what's really going on.

Thank you, Robert.