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Synchronize Your Databases with .NET Web Services (Part II)  : Page 7

When data gets created in many locations, you often need to create a process that collects and copies this data to multiple sites. In this article, you'll see how to use Web services to automatically synchronize remote databases in a decentralized way, by letting each machine query the others until they all contain the same data.




Building the Right Environment to Support AI, Machine Learning and Deep Learning

Referencing and Using a Web Service in Visual Studio
After creating a new Web Forms project in Visual Studio .NET, and building the interface Form, we get to the point where we have to consider how we are going to access a Web service on the remote machines from where we'll be collecting new rows for our database. The technique of using the WSDL.exe utility to create a proxy class, demonstrated in Part I of this article would work here, as would the technique of simply loading the Web service response as an XML document. However, Visual Studio .NET makes it far easier to work with Web services.
Figure 11. Adding Web References: The figure shows major steps in the process to add a Web Reference to a project in Visual Studio .NET.
To add a reference to the Web service to the client project, right-click the Web Reference entry in the Solution Explorer window and select Add Web Reference. As shown in Figure 11, this opens a dialog where you can search for Web services, see the default service pages that they expose, and view their contracts (the WSDL that defines the interface). The Web service you want to use is the getlogtables.asmx file described earlier in this article. This service resides in a subfolder of the local machine's default Web site, and you can navigate to it by entering its Web address or by using the right-hand pane of the dialog which is basically just a browser window.

When you click the Add Reference button to add the chosen Web service reference to your project, Visual Studio fetches the WSDL file and builds a proxy for it—just as when you use the WSDL utility directly. You can see this proxy file (named Reference.vb) in the folder that VS.NET creates under Web References (see Figure 12). You'll also see a .disco (discovery) file, and other files that VS itself requires.

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