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CHAPTER 4 ■ INSTALLING AND CREATING WCF SERVICES 121ramrameshreddy.blog.comIn addition to a sample implementation, the project references have been updated tomake it easier to work with WCF applications.Now in Solution Explorer, delete the generated Class1.cs file. Then right-click the project,and add a new item. Locate the .NET 3.0/WCF service item. Enter TradeService in the Namefield, and click Add.In the generated TradeService.cs file, replace the contents with Listing 4-8.Listing 4-8. TradeService.cs Implementationusing System;using System.ServiceModel;namespace ExchangeService{[ServiceContract(Namespace="http://PracticalWcf/Exchange/TradeService",Name="TradeService")]public interface ITradeService{[OperationContract]decimal TradeSecurity( string ticker, int quantity );}public class TradeService : ITradeService{const decimal IBM_Price = 80.50m;const decimal MSFT_Price = 30.25m;public decimal TradeSecurity( string ticker, int quantity ){if( quantity < 1 )throw new ArgumentException("Invalid quantity", "quantity" );switch( ticker.ToLower() ){case "ibm":return quantity * IBM_Price;case "msft":return quantity * MSFT_Price;default:throw new ArgumentException("SK security - only MSFT & IBM", "ticker" );}}}}ramrameshreddyramrameshreddyNotice that the top of the file contains a reference to the System.ServiceModel namespace.This namespace contains the necessary types that provide attribute support for the contractdeclaration.