Check these
Introduction to Web Services[
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Why Web Services?[
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When you need to implement things with other 3rd parties, you need web service.
Here simple example, you are developing an application(Say
Restaurant POINT OF SALE) for a client. And Client now wants to show the details in Kiosk(with options like booking items) & you never worked(just assume) in Kiosk so they are calling another person for that. And probably they need access for your database but you don't want give the access to your database. Then how? Here you need web service. Create methods(ShowItems, BookItems, etc.,) in web service & give them. So they can implement things easily.
And here a CP article
Your first C# Web Service[
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