Question

I am currently developing a WCF publish subscribe service. Is it possible for the publisher to be a asp.net application connecting to the service ? As I cant seem to find any information online about vb code for WCF.

EDIT
More details.

As my subscriber is a winform app, it is to subscribe to the WCF service using C# code and I am fine with that. the WCF Service is also coded in C# and I also have no problems with that. Normally the tutorials out in the web provides the code for a publisher to connect to the service and then call the publish code in console app or something. However all those is meant to be done in C#.

In my case, if i were to program the publisher code in a asp.net application. would it be possible?

EDIT : Codes Added

I am now currently using a C# mock publisher to post the data and the code are as follows

class Program : IPostingContractCallback
{
    static void Main(string[] args)
    {
        InstanceContext site = new InstanceContext(new Program());
        PostingContractClient client = new PostingContractClient(site);

        client.PublishPost("testing");

        Console.WriteLine();
        Console.WriteLine("Press ENTER to shut down data source");
        Console.ReadLine();

        client.Close();
    }

    public void PostReceived(string postSampleData)
    {
        Console.WriteLine("PostChange(item {0})",postSampleData);
    }
}

and for my asp.net webpage, I want all this to happen when I call this line of code

ElseIf Request.QueryString("action") = "postAlert" Then

How do I write the code as stated in above for vb? and do I just do as what I do in a C# project? adding the app.config file and the generatedProxy.cs?

Answer 1

You can do ASP.NET with VB.NET, so it’s not a case of VB vs C#.

You could very easily write an ASP.NET application and have it connect to the publish service. The ASP.NET app would connect to the publishing service the same way a console app would (i.e., creating a new proxy/client and making calls to the service).

Updated

As Jon P said, use SVCUTIL and set the language to Visual Basic, like this:

SVCUTIL.EXE /language:vb (plus your other command line arguments)

ServiceModel Metadata Utility Tool (Svcutil.exe)

You’ll want to add the <serviceModel> section to your Web.config, and generate the proxy in VB (using the /language:vb switch above).

Below is the VB version of the class you posted:

class Program Implements IPostingContractCallback

    Shared Sub Main(string[] args)

        Dim site As InstanceContext = New InstanceContext(New Program())
        Dim client AS PostingContractClient = New PostingContractClient(site)

        client.PublishPost("testing")

        Console.WriteLine()
        Console.WriteLine("Press ENTER to shut down data source")
        Console.ReadLine()

        client.Close()
    End Sub

    Public Sub PostReceived(ByVal postSampleData As String)

        Console.WriteLine("PostChange(item {0})", postSampleData)
    End Sub
End Class

Your ASP.NET app is acting as the publisher, but it’s connecting to the publishing service (if I understand correctly), so all it’s really doing is making a call to the service to publish the post.

The service itself should handle the callback and “publish” the event on the callback channel(s) for the subscriber.

So (without all the code for the various components I might be missing something – if I am, please let me know so I can update accordingly), all your ASP.NET app needs to do is:

Dim client As PostingContractClient = New PostingContractClient()
client.PublishPost("testing")
client.Close()

To reiterate (again, based on my understanding):

1. ASP.NET app calls the publishing service to publish the post.
2. The publishing service receives the post, and calls the callback method for all active subscribers.
3. Your subscribed client (the WinForm) receives the callback and processes it accordingly.

So for part 2, you might have something like:

public void PublishPost(string post)
{

    // Do something with the post

    callback.PostReceived(string postSampleData);

    // callback is a callback channel of type IPostingContractCallback
    // i.e:
    // IPostingContractCallback calback = OperationContext.Current.GetCallbackChannel<IPostingContractCallback>();
}

The client(s) should then pick up the PostReceived “event” and do what their implementation of the callback interface specifies.