How do I "concretise" an open generic for WCF ?

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(Looking for thoughts...)

So - when you create a WCF service with a [ServiceContract()] and [DataContract()] you can't use open generics - which I do understand why.

However - anyone have any ideas about how I could specify a small set of types and have the generics turned into concrete implementations in the service ? (Probably looking at codegen??)

i.e. if I have a function like

VB

Add(Of TParam)(Byval lhs As TParam, ByVal rhs As TParam) As TParam

I'd like it to generate:-

VB

AddInteger(Byval lhs As Integer, Byval rhs As Integer) As Integer

AddDouble(Byval lhs As Double, Byval rhs As Double) As Double

(etc.)

Posted 26-Mar-14 0:26am

Duncan Edwards Jones

Updated 26-Mar-14 7:13am

Matt T Heffron

v3

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Matt T Heffron 26-Mar-14 12:40pm

Did you mean WCF?
ServiceContract and DataContract have nothing to do with WPF

Duncan Edwards Jones 26-Mar-14 13:09pm

yeah - WCF it is... corrected.

Matt T Heffron 26-Mar-14 13:13pm

I fixed the "tag" also...

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Sergey Alexandrovich Kryukov · Answer 1 · 2014-03-26T09:13:00

Solution 1

This is not related to WCF either. You just need to learn how generics work in general and the syntax for their declaration and instantiation, as well as the type inference. Please see:
http://msdn.microsoft.com/en-us/library/ms235246.aspx[^].

—SA

Posted 26-Mar-14 9:13am

Sergey Alexandrovich Kryukov

Duncan Edwards Jones · Answer 2 · 2014-03-26T09:45:00

As it happens I have just explicitly declared the interfaces for the specific types I want to handle and passed them on to the generic code the other side of the WCF service contract e.g.

VB

''' <summary>
 ''' Get the active clients on the system
 ''' </summary>
 ''' <param name="query">
 ''' The query specification for getting the active clients
 ''' </param>
 ''' <returns>
 ''' A set of client records in JSON form
 ''' </returns>
 <operationcontract()>
 <webget(responseformat:>
 Function GetActiveClients(ByVal query As GetActiveClientsQueryDefinition) As IReadOnlyList(Of ClientSummary)

and the implementation of this is:-

VB

Public Function GetActiveClients(query As GetActiveClientsQueryDefinition) As IReadOnlyList(Of ClientSummary) Implements IQueryHandlerService.GetActiveClients
    If (m_queryHandler IsNot Nothing) Then
        Return m_queryHandler.Handle(query)
    Else
        'Return an empty list
        Return New List(Of ClientSummary)()
    End If
End Function

where m_queryHandler.Handle is the generic function :-

VB

''' <summary>
''' Handle the given query definition and return the results
''' </summary>
''' <typeparam name="TResult">
''' The type of the result
''' </typeparam>
''' <param name="query">
''' The query definition to handle
''' </param>
Public Function Handle(Of TResult)(query As Query.IQueryDefinition(Of TResult)) As TResult

    Dim handler = GetHandler(Of TResult)(query)

    If (handler IsNot Nothing) Then
        Return handler.Handle(query)
    Else
        ' Could not find and appropriate handler
        Return Nothing
    End If

End Function