>>Double whammy :-}
>>
>>(a) The C# code must have been wrong
>>(b) Even if it was correct the converter would fail.
>
>This came from Microsoft:
>
>http://msdn.microsoft.com/en-us/library/system.servicemodel.channels.messageencodingbindingelement(v=vs.110).aspx

Ah. I compiled that (after digging up a matching implementation of CustomTextMessageEncoder here http://msdn.microsoft.com/en-us/library/ms751486(v=vs.110).aspx)

Seems that C# inherits the constraint from the base class - if I add it to the BuildChannelListener method I get an error :
"Constraints for explicit interface implementation method are inherited from the base method, so they cannot be specified directly"

I guess VB.NET doesn't work that way - i.e. they *have* to be specified :-{