Visual Basic.NET How to Program (PDF)

Chapter 21 ASP .NET and Web Services 1045
The next example demonstrates how to create a Web-service client and its corresponding
proxy class. We must begin by creating a project and then adding a Web reference
to the project. When we add a Web reference to a client application, the proxy class is created.
The client then creates an instance of the proxy class, which is in turn used to call
methods included in the Web service.
To create a proxy in Visual Studio, right click the References folder in Solution
Explorer, and select Add Web Reference (Fig. 21.8). In the Add Web Reference
dialog that appears (Fig. 21.9), enter the Web address of the Web service, and press Enter.
In this chapter, we store the Web service in the root directory of our local Web server
(http://localhost, whose physical location is C:\Inetpub\wwwroot). We do
not store the services in the VB directory used in the previous chapter. For simplicity, we
have instead stored them directly in the root of our Web server. This allows us to add a Web
reference without typing in the whole address, by clicking the link Web References on
Local Web Server (Fig. 21.9). Next, we select the appropriate Web service from the list
of Web services located on localhost (Fig. 21.10). Notice that each Web service is
listed as a file with the extension .vsdisco, located in the directory for the Web service
project. Files with the extension .disco and .vsdisco are known as discovery files.
We discuss discovery files, as well as the distinction between discovery files with the
.disco and .vsdisco extension later in this section. When the description of the Web
service appears, click Add Reference (Fig. 21.11). This adds to the Solution Explorer
(Fig. 21.12) a Web References folder with a node named after the domain name where
the Web service is located. In this case, the name is localhost, because we are using the
local Web server. This means that, when we reference class HugeInteger, we will be
doing so through class HugeInteger in namespace localhost (the Web service class
and proxy class have the same name). Visual Studio generates a proxy for the Web service
and adds it as a reference (Fig. 21.12).
Fig. 21.8 Adding a Web service reference to a project.