Use UnityConfiguration to automatically wire up constructors?

[Merrion]

I have a CQRS architecture which, on the query side has a QueryDefinition class and for each of them a QueryHandler class.

I had been wiring them up 1-1 in a configuration file but I would rather use some sort of auto-discovery for example the nugget package UnityConfiguration.

How do I configure it such that when a QueryHandler is created if that handler requires one or more repository classes they will be instantiated and passed into the constructor?

For example - my query handler for the "Get all clients" query would look something like:-

Imports TaskBazaar.Query
Imports TaskBazaar.Repository
 
Namespace Handlers
    Public Class GetActiveClientsQueryHandler
        Implements IQueryHandler(Of Definitions.GetActiveClientsQueryDefinition, IReadOnlyList(Of DTO.ClientSummary))
 
 
        Private ReadOnly m_readRepository As IClientReadRepository
 
        Public Function Handle(query As Definitions.GetActiveClientsQueryDefinition) As IQueryResponse(Of IReadOnlyList(Of DTO.ClientSummary)) Implements IQueryHandler(Of Definitions.GetActiveClientsQueryDefinition, IReadOnlyList(Of DTO.ClientSummary)).Handle
 
            If (m_readRepository IsNot Nothing) Then
                Dim dtoConverter As New Converter(Of TaskBazaar.Repository.ClientRecord, DTO.ClientSummary)(AddressOf ConvertToDTO)
                Return m_readRepository.GetWhere(Function(f As ClientRecord) (f.Active = True)).Values.ToList.ConvertAll(dtoConverter)
            Else
                Throw New MissingRepositoryException("IClientReadRepository")
            End If
 
        End Function
 
        ''' <summary>
        ''' Create a new handler for the active clients query using the given repository
        ''' </summary>
        ''' <param name="readRepository">
        ''' The read repository to use to retrieve the data
        ''' </param>
        Public Sub New(ByVal readRepository As IClientReadRepository)
            m_readRepository = readRepository
        End Sub
 
    End Class
End Namespace

As you can see it must take an IClientReadRepository in the constructor.

I populate the unity container thus:-

Public Shared Sub RegisterTypes(container As IUnityContainer)
 
        Dim interfaceType As Type = Nothing
 
        'Get any repository handlers...we will use the namespace to differentiate between back end technologies
        interfaceType = GetType(IRepositoryRead(Of ,))
 
        container.RegisterTypes(AllClasses.FromAssembliesInBasePath(includeUnityAssemblies:=False, includeSystemAssemblies:=False).Where(Function(z) z.Namespace.Contains("Azure")).Where(Function(t) t.ImplementsInterface(interfaceType)),
             getFromTypes:=Function() WithMappings.FromMatchingInterface(interfaceType),
             getName:=Function(i) WithName.TypeName(i),
             getLifetimeManager:=Function(i) WithLifetime.PerThread(i)
                                )
 
        'Get the interface definition for the generic query handler interface we are looking for
        interfaceType = GetType(IQueryHandler(Of ,))
 
        container.RegisterTypes(AllClasses.FromAssembliesInBasePath(includeUnityAssemblies:=False, includeSystemAssemblies:=False).Where(Function(t) t.ImplementsInterface(interfaceType)),
              getName:=Function(i) GetNameFromQueryDefinition(i),
              getLifetimeManager:=Function(i) WithLifetime.PerThread(i),
              getInjectionMembers:=Function(i) GetConstructorInjections(i))
 
 
 
    End Sub

But what do I need to put in the GetConstructorInjections so it knows to create the ClientRepository when it creates the GetActiveClientsQueryHandler?

e.g. what goes in :-

Private Shared Function GetConstructorInjections(i As Type) 
           As IEnumerable(Of InjectionMember)
 
  ' Get the constructor for i that has any
  ' IReadRepository derived parameters
 
 
    End Function

[Evil_Giraffe]

You shouldn't need to do anything. Unity will attempt automatic constructor injection. Does Unity know about your IClientReadRepository implementation?

[Merrion]

It does, yes - the first set of registrations includes it:

'Get any repository handlers...we will use the namespace to differentiate between back end technologies
 
        interfaceType = GetType(IRepositoryRead(Of ,))
 
        container.RegisterTypes(AllClasses.FromAssembliesInBasePath(includeUnityAssemblies:=False, includeSystemAssemblies:=False)
                .Where(Function(z) z.Namespace.Contains("Azure")).Where(Function(t) t.ImplementsInterface(interfaceType)),
            getFromTypes:=Function() WithMappings.FromMatchingInterface(interfaceType),
             getName:=Function(i) WithName.TypeName(i),
             getLifetimeManager:=Function(i) WithLifetime.PerThread(i)
                                )

But in fact my IClientReadRepository itself inherits IRepositoryRead(Of Client, Integer)).. maybe this extra step is befuddling it.