>>Maybe;

    Public Overrides Function BuildChannelListener(Of TChannel As {Class, IChannel})(context As BindingContext) _
>>As IChannelListener(Of TChannel)
>>        If context Is Nothing Then
>>            Throw New ArgumentNullException("context")
>>        End If
>>
>>        context.BindingParameters.Add(Me)
>>        Return context.BuildInnerChannelListener(Of TChannel)()
>>    End Function

>
>This syntax is not accepted in VB.NET. I see the designer showing a bad code under {.

Compiles OK for me with VS2012 targeting 4.5. What version of VS and .NET are you using?