This article provides a summary of how to expose existing DotNetNuke modules as a Web service to any consumer.

Recently we released a Web service version of the WWWCoder.com Resource Directory. Basically this module allows you to insert our directory into your DotNetNuke site. In this article we're going to cover some basic concepts on how to expose modules you have written as a Web service in DotNetNuke. Our entire directory service took around 8 hours to complete. That's pretty quick considering we released a private assembly and fully functional directory with keyword searching, paging, categorical listings, etc. Ok enough of our bragging, lets move on to the code.

We're going to assume for this article that you're familiar with writing modules for DotNetNuke. So you understand what a Private Assembly is, stored procedures, code behind pages, and your moduleDB.vb class for calling your stored procedures.

The first thing you need to do is create a Web service class as part of your module project you want to expose as a Web service. You could also create a new project explicitly for the Web service class if you want. Once you create your WebService.asmx.vb class, you need to create wrapper methods to expose your moduleDB.vb class files to the world.

Creating a Web Service Class

Let's go over the basics of our Web service class and some DNN considerations:

Imports System.Web.Services
::
::
Namespace DotNetNuke
'here is where we declare our namespace so clients can _
'create a reference to the Web service.
<System.Web.Services.WebService(Namespace:="http://tempuri.org//MyWebService")> _
  Public Class MyWebService
    Inherits System.Web.Services.WebService
::
::
::
  End Class
End Namespace

Now that we have our class structure and we're have our DotNetNuke namespace, we'll expose some of our methods we created for our module's moduleDB.vb class file.

<WebMethod()> _
Public Function GetCategories(ByVal inParentID As Integer) As DataSet
  Dim objCategories As New ASPSearchDB
  Dim dsCategories As DataSet = _
     ConvertDataReaderToDataSet(objCategories.GetCategories(thisModule, _
     inParentID, True))
  Return dsCategories
End Function

The previous method is a method that is contained in our DB class file for our existing module. Now if you've done some module development in DNN, you've probably used mostly SQLDataReaders to bind to a Data List or Data Grid. With Web services though you can't return a Data Reader, the great thing however, is DNN provides you with a method to convert your readers to Data Sets. Nice hunh? So all we did in the previous method was call our existing method to return our category listings just as it does in our regular DNN module, and then wrap that call with the DNN method ConvertDataReaderToDataSet, then return the converted Data Set to the requesting client via our exposed Web method.

Believe it or not it really is that simple to create a Web service in DNN. Some caveats we ran into was to hard code our module IDs and other values to pass to our Web service, but these could very well be exposed by your Web service class and then let the client pass these values to ensure you're requesting the correct module data from DNN.

On the Client

As for the client piece it is just as easy. Another thing I want you to consider is, now that you have exposed your DNN module as a Web service, don't limit yourself to exposing DNN data to just other DNN portals. We have plans to expose to IBuySpy, and any .Net or SOAP enabled client. This way our directory running under DNN gets exposed as a service to anyone requesting it. Web services allow you to share your data with any application. Can you imagine, DNN modules running in Perl on a Linux box?

To consume the service, in our example we created a new DNN module and compiled it into a private assembly. To set up the project we added a new project to our DNN project, and then added a Web reference to our Web service. You do this in Visual Studio, by right clicking on your project references and select Web Reference. You'll then be prompted to enter in a URL of your Web service class file. Once the reference is created you can then work with it in Visual Studio like any other object. Intellisense and all.

In our DNN module class we then create a reference to the Web service like so:

Dim objWS As New com.wwwcoder.www.MyWebService

Now that the MyWebService is instantiated in our class we can refer to the previous method GetCategories and bind the resulting Data Set to a Data List like so:

::
::
DataList1.DataSource = objWS.GetCategories(CType(viewstate("parentid"), _
    Integer))
DataList1.DataBind()

That's all there is to it, then proceed to write your module as you would any other module.

By: Patrick Santry, Microsoft MVP (ASP/ASP.NET), developer of this site, author of books on Web technologies, and member of the DotNetNuke core development team. If you're interested in the services provided by Patrick, visit his company Website at Santry.com.