Very Specific C# to VB.NET Conversion Problem

Question

I am currently working on a project which uses the AutoFac Inversion of Control container.

I am attempting to convert some example code from C# into a codebase of an existing project of mine which is written in VB.NET and I've hit a problem.

The original line of code is:

EventHub.Subscribe<HandshakingEvent>(container.Resolve<HandshakeAuthenticator>().CheckHandshake);

Which I have converted to:

EventHub.Subscribe(Of HandshakingEvent)(Container.Resolve(Of HandshakeAuthenticator)().CheckHandshake)

But - this is causing an error, "Argument not specified for parameter 'ev' of CheckHandshake".

The type of the parameter for the EventHub.Subscribe(Of HandshakingEvent) procedure is System.Action (of HandshakingEvent)

I can see what the problem is, I'm just not really sure what to do about it! I've tried using 'AddressOf', but that doesn't seem to work, either.

Thanks in advance... - Chris

What's CheckHandshake?

SLaks
– SLaks

2010-11-07 23:48:53 +00:00
Commented Nov 7, 2010 at 23:48 — SLaks
– SLaks, Commented Nov 7, 2010 at 23:48

SLaks · Accepted Answer · 2010-11-07 23:48:44Z

5

Try

EventHub.Subscribe(Of HandshakingEvent)(AddressOf Container.Resolve(Of HandshakeAuthenticator)().CheckHandshake)

(using the AddressOf keyword to get a delegate)

answered Nov 7, 2010 at 23:48

SLaks

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Chris Roberts Over a year ago

Thanks - You're spot on. I had tried 'AddressOf', but it still didn't work. It turns out it was for a different reason, though! I had declared the parameter of CheckHandshake as ByRef, not ByVal!

Guffa · Accepted Answer · 2010-11-08 00:36:06Z

3

The VB code is trying to call the method instead of creating a delegate for it. Use the AddresOf operator to get a deletegate:

EventHub.Subscribe(Of HandshakingEvent)(AddressOf Container.Resolve(Of HandshakeAuthenticator)().CheckHandshake)

The keyword is not needed in C#, as parentheses are always used when you call a method, but in VB you can call a method without parentheses also.

edited Nov 8, 2010 at 0:36

answered Nov 7, 2010 at 23:49

Guffa

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1 Comment

Chris Roberts Over a year ago

Thanks - You're spot on. I had tried 'AddressOf', but it still didn't work. It turns out it was for a different reason, though! I had declared the parameter of CheckHandshake as ByRef, not ByVal!

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