Common Interfaces using VB.NET

In this article I will explain you about Common Interfaces using VB.NET.
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Let's see another aspect of .NET Remoting. This will put you in mind of the COM+ style of remote object usage. We will develop an example using a shared interface. The interfaces also afford us a good means for using black-box objects. We have used this feature with type library (TLB) files with COM+ objects. To develop against a type library is sufficient to use services on a COM server. The client calls GetObject on an endpoint without knowing what the exact object type is; all it knows is that the object implements an interface. This illustrates how we can build a client that does not reference a server object at compile-time. The sample code for this example consists of four parts: a shared interface, the remote object that implements this interface, a server, and a client that will use this interface method via an unknown object. Listing 23.17 displays the code for the shared interface.

Listing 23.17: SOAP Shared Interface3 (Listing23.17.VB)

    Imports System
    Namespace ExampleRemoting
         
Public Interface IDateTime
               
Function DateTimeMethod(name As [String]) As String
         
End Interface
    End Namespace

Listing 23.18 contains the code for the object that implements the shared interface.

Listing 23.18: SOAP Object That Implements Share 3 (Listing23.18.VB)

    Namespace ExampleRemoting
        Public Class DateTimeServer
            Inherits MarshalByRefObject
            Implements IDateTime
            Public Sub New()
                Console.WriteLine("DateTime server activated")
            End Sub
            Protected Overrides Sub Finalize()
                Try
                    Console.WriteLine("DateTime server Object Destroyed")
                Finally
                    MyBase.Finalize()
                End Try
            End Sub
            Public Function DateTimeMethod(ByVal name As [String]) As [String]
                Dim strMessage As [String] = "Hi " + name + ". Here is the current DateTime: " + DateTime.Now
                Console.WriteLine(strMessage)
                Return strMessage
            End Function
        End Class
    End Namespace

The code for the server that delivers the remote methods appears in Listing 23.19.

Listing 23.19: SOAP Server3 (Listing23.19.VB)

    Imports System
    Imports System.Runtime.Remoting
    Imports System.Runtime.Remoting.Channels
    Imports System.Runtime.Remoting.Channels.Http
    Namespace ExampleRemoting
        Public Class Example
            Public Shared Sub Main()
                Dim channel As New HttpChannel(8888)
                ChannelServices.RegisterChannel(channel)
                RemotingConfiguration.RegisterWellKnownServiceType(Type.[GetType]("ExampleRemoting.DateTimeServer, Object3"), "SayDateTime",
                WellKnownObjectMode.SingleCall)
                System.Console.WriteLine("press <enter> to exit.")
                System.Console.ReadLine()
            End Sub
        End Class
    End
Namespace

Listing 23.20 shows the code for the client that connects to the server and uses the methods exposed.

Listing 23.20: SOAP Client3 (Listing23.20.VB)

    Imports System
    Imports System
    Imports System.Runtime.Remoting
    Imports System.Runtime.Remoting.Channels
    Imports System.Runtime.Remoting.Channels.Http
    Namespace ExampleRemoting
        Public Class Client
            Public Shared Sub Main()
                Dim channel As New HttpChannel()
                ChannelServices.RegisterChannel(channel)
                ' create an object of type interface
                Dim obj As IDateTime = DirectCast(Activator.GetObject(GetType(ExampleRemoting.IDateTime), "http://127.0.0.1:8888/SayDateTime"), IDateTime)
                If obj = Nothing Then
                    Console.WriteLine("could not locate server!")
                Else
                    Console.WriteLine(obj.DateTimeMethod("Bozo the clown"))
                End If
            End Sub
        End Class
    End Namespace
    Namespace ExampleRemoting
        Public Class Client
            Public Shared Sub Main()
                Dim channel As New HttpChannel()
                ChannelServices.RegisterChannel(channel)
                ' create an object of type interface
                Dim obj As IDateTime = DirectCast(Activator.GetObject(GetType(ExampleRemoting.IDateTime), "http://127.0.0.1:8888/SayDateTime"), IDateTime)
                If obj = Nothing Then
                    Console.WriteLine("could not locate server!")
                Else
                    Console.WriteLine(obj.DateTimeMethod("Bozo theclown"))
                End If
            End Sub
        End Class
    End Namespace

Conclusion

Hope this article would have helped you in understanding Common Interfaces using VB.NET.

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