Web Services are cool; web methods are all the rage. But are they just another cool technology du jour, a flash-in-the-pan? If we ignore them long enough, will they just go away? No, this technology has staying power written all over it. It is not just hype. Web services are a genuinely useful blade in your Swiss Army Knife of development techniques. In what way?

Leveraging web services, you don't need to reinvent the wheel for functions that are rare enough to not be part of your programming language's built-in functions or development tool's rtl, but are nevertheless common enough to be useful to many--or at least several--developers. Also, in many cases the return values of web services are dynamic, such as the weather at a given zip code, the current time, prices for this or that item, road conditions, etc. In cases like these you will need to access some source of dynamic information anyway (read "the Internet"), so there are little or no performance drawbacks in consuming a web service that has already been created to provide the information your application needs.

In this example, we will create a web service (in .NETspeak, a "web method") that returns the day of the week for any given date. We will also create a WinForm client that passes the requisite year, month, and day values to the web method.

Creating the Web Method/Service

Let's jump right in. Select File | New | Other | ASP.NET Web Service Application

Change Name to "DOW" (no, not after the actor who portrayed The Beaver's older brother Wally (Tony Dow), but for Day Of the Week)).

Two files are created for you: WebService1.asmx, and WebService1.asmx.cs. Select File | Save As, and save WebService1.asmx as DOW.asmx. This will also change the *.cs file to DOW.asmx.cs.

If you try to run the project at this point, you'll get the error message "unable to attach to ASP.NET process (typically aspnet_wp.exe)." Right-click DOW.asmx in the Project Manager and select "Set as start page". Now if you run it, you will get a page in IE like this:

Change the default name of your Web Method (WebService1) in both the *.asmx and the *.asmx.cs file to DOW. Also, add the following attribute (replacing my name with yours) above

[WebService(Namespace="http://www.ClayShannon.com"]

Remove the placeholder web methods (commented out) in the DOW.asmx.cs file, and add the following method and attribute at the bottom of the unit:

[WebMethod]
public string GetDow(int intYear, int intMonth, int intDay)
{
  DateTime d8 = new DateTime(intYear, intMonth, intDay, new GregorianCalendar());
  GregorianCalendar gregCal = new GregorianCalendar();

  return gregCal.GetDayOfWeek(d8).ToString();
}

Also, add the following at the top of the unit:

Using System.Globalization;

That's all there is to it. Now, when you run the app, you will see this screen in your web browser (IE in my case):

Clicking ServiceDescription displays the SOAP XML behind the web method:

Clicking GetDow displays this page:

If that isn't slick, I don't know what is: C#Builder allows you to test your web method from within the web method/service itself. You don't have to create a client first to test it-what a time-saver, since otherwise you might have to switch back and forth between this project and the client project!

Here's a screenshot of the results I got after entering some test data and then selecting the Invoke button:

Creating the Client

Select File | New | C# Application. A WinForm will display in the designer.

Select Project | Add Web Reference The UDDI browser dialog will display:

Enter the following into the URL edit box at the top of the dialog:

http://localhost/DOW/DOW.asmx

Select the "Go" (right-arrow) button to the left of the URL edit box. The progress bar and its affiliated label at the Southwest corner of the UDDI dialog will let you know it's opening that page. It will then show you the same HTML page as seen previously in your web browser:

Select the Add Reference button. This adds some files to your project. You can see this in the Project Manager-expand the References, Web Reference, and Local Host nodes to view what has been created and added to your project for you. System.XML.dll has been added as a child to the References node, DOW.wsdl as well as Reference.map have been added to the localhost node, and the Reference.cs source code file has been added below Reference.map.

Add the Web method you created earlier to your client application's References by selecting Project | Add Reference | Project References, and then selecting the Browse button to navigate to the DOW.dll file. Now add using DOW; to the using clause of your main form (named WinForm.cs by default).

private void button1_Click(object sender, System.EventArgs e)
{
  int AYear = Convert.ToInt32(this.tbYear.Text);
  int AMonth = Convert.ToInt32(this.tbMonth.Text);
  int ADay = Convert.ToInt32(this.tbDay.Text);

  try
  {
    DOW localdow = new DOW();
    MessageBox.Show(localdow.GetDow(AYear, AMonth, ADay));
  }
  catch (Exception x)
  {
    MessageBox.Show(x.Message, 
      "Something is rotten in Denmark!");
  }
}

We know have a working web method/service and a client that uses, or "consumes" it. Beyond the scope of this article is the next obvious step of publishing, or exposing the web method on a Web Service hosting site such as www.xmethods.com.