Microsoft created the WCF (Windows Communication Foundation) framework to create service-oriented applications. It enables the transmission of data as asynchronous messages between service endpoints. IIS, Windows services, or even self-hosted apps can host these endpoints. Using a variety of protocols, such as HTTP, TCP, Named Pipes, or MSMQ, developers can create secure, dependable, and transactional services with WCF.

Important WCF Features

• Interoperability: Uses JSON, REST, or SOAP to easily interface with other platforms.
• Multiple Message Patterns: Facilitates duplex, one-way, and request-reply communication.
• Security: Integrated authorization, authentication, and encryption.
• Transaction Support: Guarantees dependable rollback and message delivery.
• Flexible Hosting: Use a console application, Windows Service, or IIS to host.
• Extensibility: It is simple to implement custom behaviors, bindings, and contracts.

Overview of the WCF Architecture
A WCF service is built around four key concepts:

Example: Simple WCF Service

Let’s create a simple “Calculator Service” using WCF.

Step 1. Define the Service Contract
using System.ServiceModel;

[ServiceContract]
public interface ICalculatorService
{
    [OperationContract]
    int Add(int a, int b);

    [OperationContract]
    int Subtract(int a, int b);
}

Step 2. Implement the Service
public class CalculatorService : ICalculatorService
{
    public int Add(int a, int b) => a + b;
    public int Subtract(int a, int b) => a - b;
}

Step 3. Configure Service in App.config
<system.serviceModel>
  <services>
    <service name="WCFDemo.CalculatorService">
      <endpoint address="" binding="basicHttpBinding" contract="WCFDemo.ICalculatorService" />
      <host>
        <baseAddresses>
          <add baseAddress="http://localhost:8080/CalculatorService"/>
        </baseAddresses>
      </host>
    </service>
  </services>
  <behaviors>
    <serviceBehaviors>
      <behavior>
        <serviceMetadata httpGetEnabled="true"/>
        <serviceDebug includeExceptionDetailInFaults="true"/>
      </behavior>
    </serviceBehaviors>
  </behaviors>
</system.serviceModel>

Step 4. Host the Service (Console Example)
using System;
using System.ServiceModel;

class Program
{
    static void Main()
    {
        using (ServiceHost host = new ServiceHost(typeof(CalculatorService)))
        {
            host.Open();
            Console.WriteLine("WCF Calculator Service is running...");
            Console.WriteLine("Press any key to stop.");
            Console.ReadKey();
        }
    }
}

Step 5. Consume the Service (Client Side)
Add a Service Reference in your client project → Enter the service URL (e.g., http://localhost:8080/CalculatorService?wsdl).

Then, you can use:
var client = new CalculatorServiceClient();
Console.WriteLine(client.Add(10, 20));  // Output: 30

Benefits of Using WCF

Common WCF Bindings

Conclusion

WCF remains a powerful framework for building service-oriented, secure, and scalable communication systems.
While modern APIs often use ASP.NET Core Web APIs or gRPC, WCF continues to be a great choice for enterprise-grade distributed applications that require SOAP, WS-Security, and transactional messaging.