IntroductionFirst of all, let me tell you that I am not a C# expert. I am primarily a Java developer but have been experimenting C# and the .NET platform. Basically I am developing a SOAP Web Service using Java and Apache SOAP, and have decided to give my clients an option when and how they access the service. Hence I am going to provide a Web/JSP user interface and a native Windows application written in C#. My main motivation for writing this article is that fact that I could not find anything else like it on the web. There were plenty of articles telling me how I can use the Apache SOAP API to use a .NET^TM service, but not the other way round.
We'll start with a refresher on some of the terminology I will be using:

• SOAP:- Simple Object Access Protocol (SOAP) is a way for a program running in one kind of operating system (such as Windows 2000) to communicate with a program in the same or another kind of an operating system (such as Linux) by using the World Wide Web's Hypertext Transfer Protocol (HTTP)and its Extensible Markup Language (XML) as the mechanisms for information exchange
• Apache SOAP:- The Apache Foundations implementation of the SOAP protocol written in Java.
• C#:- C# (pronounced "C-sharp") is a new object-oriented programming language from Microsoft, which aims to combine the computing power of C++ with the programming ease of Visual Basic. C# is based on C++ and contains features similar to those of Java.

Please note that this document does not covering installing Apache Tomcat, Apache SOAP or the .NET^TM SDK. See the resources section for more information and links to all these projects.

Summary

In order to make use of a Apache SOAP web service using C# you need to do the following steps:

1. Create a proxy class that implements all the methods you want to be able to call from your client. This class needs to extend the System.Web.Services.Protocols.SoapHttpClientProtocol
2. The constructor of this class needs to set the URL property of the above class. Basically this will be the URL of the Apache SOAP rpcrouter servlet e.g. http://localhost:8080/apache-soap/servlet/rpcrouter
3. The proxy class needs to have a WebServiceBindingAttribute set. This defines the name of the web service and the namespace that the service is to use. The Name is usually the ID of the Apache SOAP Service. The namespace is usually the URL of the server hosting the service.
4. You will need to define a method in the proxy for each method that the service supports and the client wants to use. This method will need to match the signature of the method in the web service itself i.e. if your service defines a method called deleteItem which takes a string as an argument, you will need to define a method in the proxy class called deleteItem(string id).
5. Each method will need to have an associated SoapDocumentMethodAttribute, this defines the SOAPAction, as well as the name of the Apache SOAP Service that you are connecting to. It also defines the XML encoding style and how the parameters are formatted in the body of the SOAP request.
6. Each method will then make use of the Invoke method provided by the SoapHttpClientProtocol class to actually call the method on the web service and get the result.
7. Your client class will then simply need to create an instance of the proxy you have just created, and make calls on the method that it implements, the proxy handles sending the requests to the Apache SOAP server and retrieving the results.

Details

Ok let's get down to business, the above list gave you a brief overview of the process, I am now going to expand on it and show you the code that I used to talk to my service.

The Service

I'll start by giving you the code to my Apache SOAP service:

package com.konnect.soap;public class HelloService{    public String hello(St