How to: Implement a Windows Communication Foundation Service Contract

This is the second of six tasks required to create a basic Windows Communication Foundation (WCF) service and a client that can call the service. For an overview of all six tasks, see the Getting Started Tutorial topic.

Creating a WCF service requires that you first create the contract, which is defined using an interface. For more information about creating the interface, see How to: Define a Windows Communication Foundation Service Contract. The next step, shown in this example, is to implement the interface. This involves creating a class called CalculatorService that implements the user-defined ICalculator interface. The code used for this task is provided in the example following the procedure.

To implement a WCF service contract

Create a new class called CalculatorService in the same file where you defined the ICalculator interface. The CalculatorService implements the ICalculator interface.
C#
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```
public class CalculatorService : ICalculator
```

Implement each method defined in the ICalculator interface within the CalculatorService class.

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public double Add(double n1, double n2)
{
    double result = n1 + n2;
    Console.WriteLine("Received Add({0},{1})", n1, n2);
    // Code added to write output to the console window.
    Console.WriteLine("Return: {0}", result);
    return result;
}

public double Subtract(double n1, double n2)
{
    double result = n1 - n2;
    Console.WriteLine("Received Subtract({0},{1})", n1, n2);
    Console.WriteLine("Return: {0}", result);
    return result;
}

public double Multiply(double n1, double n2)
{
    double result = n1 * n2;
    Console.WriteLine("Received Multiply({0},{1})", n1, n2);
    Console.WriteLine("Return: {0}", result);
    return result;
}

public double Divide(double n1, double n2)
{
    double result = n1 / n2;
    Console.WriteLine("Received Divide({0},{1})", n1, n2);
    Console.WriteLine("Return: {0}", result);
    return result;
}

Note:
The write output code has been added to make testing convenient.

Example

The following code example shows both the interface that defines the contract and the implementation of the interface.

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using System;
using System.ServiceModel;

namespace Microsoft.ServiceModel.Samples
{
    // Define a service contract.
    [ServiceContract(Namespace = "http://Microsoft.ServiceModel.Samples")]
    public interface ICalculator
    {
        [OperationContract]
        double Add(double n1, double n2);
        [OperationContract]
        double Subtract(double n1, double n2);
        [OperationContract]
        double Multiply(double n1, double n2);
        [OperationContract]
        double Divide(double n1, double n2);
    }

    // Step 1: Create service class that implements the service contract.
    public class CalculatorService : ICalculator
    {
         // Step 2: Implement functionality for the service operations.
        public double Add(double n1, double n2)
        {
            double result = n1 + n2;
            Console.WriteLine("Received Add({0},{1})", n1, n2);
            // Code added to write output to the console window.
            Console.WriteLine("Return: {0}", result);
            return result;
        }

        public double Subtract(double n1, double n2)
        {
            double result = n1 - n2;
            Console.WriteLine("Received Subtract({0},{1})", n1, n2);
            Console.WriteLine("Return: {0}", result);
            return result;
        }

        public double Multiply(double n1, double n2)
        {
            double result = n1 * n2;
            Console.WriteLine("Received Multiply({0},{1})", n1, n2);
            Console.WriteLine("Return: {0}", result);
            return result;
        }

        public double Divide(double n1, double n2)
        {
            double result = n1 / n2;
            Console.WriteLine("Received Divide({0},{1})", n1, n2);
            Console.WriteLine("Return: {0}", result);
            return result;
        }
    }
}

Now the service contract is created and implemented. Build the solution to ensure there are no compilation errors and then proceed to How to: Host and Run a Basic Windows Communication Foundation Service to run the service. For troubleshooting information, see Troubleshooting the Getting Started Tutorial.

Compiling the Code

If you are using a command-line compiler, you must reference the System.ServiceModel assembly.