Here’s a comparison of Web API, Web Service, and WCF, breaking down their key characteristics and differences:

1. ASP.NET Web API

• Purpose:
  A framework designed to build RESTful HTTP services.

• Key Features:

  • Built specifically for HTTP and RESTful principles.
  • Supports content negotiation (JSON, XML, etc.).
  • Lightweight, stateless, and easy to integrate with modern web apps and mobile devices.

• Protocols:

  • HTTP/HTTPS only.

• Serialization:

  • Default support for JSON and XML.

• Hosting:

  • IIS, self-hosting, containers, or cloud platforms like Azure.

• When to Use:

  • When building REST APIs for web or mobile apps.
  • For lightweight, stateless communications over HTTP.

2. Web Service (ASMX Services)

• Purpose:
  A legacy approach to create SOAP-based services using XML for communication.

• Key Features:

  • Simple to set up but limited to HTTP.
  • Only supports SOAP for communication.
  • Typically tied to .NET applications.

• Protocols:

  • HTTP only.

• Serialization:

  • Uses XML for message formatting.

• Hosting:

  • IIS only.

• When to Use:

  • In legacy systems that require SOAP-based communication.
  • For simple services within .NET environments.

3. Windows Communication Foundation (WCF)

• Purpose:
  A flexible framework for building service-oriented applications supporting multiple protocols.

• Key Features:

  • Supports SOAP-based and RESTful services (though REST requires configuration).
  • Advanced features like transactions, security, and duplex communication.
  • High flexibility in communication protocols.

• Protocols:

  • HTTP, TCP, Named Pipes, MSMQ, and more.

• Serialization:

  • Default DataContractSerializer (supports XML, can be configured for JSON).

• Hosting:

  • IIS, self-hosting, Windows Services.

• When to Use:

  • When communication requires multiple protocols or enterprise-grade features.
  • For complex distributed systems with advanced requirements (e.g., message queuing, security, duplex communication).

Comparison Table

Key Takeaways

• Web API is the go-to choice for building RESTful services in modern applications.
• Web Services are simpler but limited to SOAP and HTTP, best for older systems.
• WCF is powerful and versatile but more complex, suited for enterprise-grade, multi-protocol systems.