Types of APIs Based on Functionality

APIs (Application Programming Interfaces) help different software systems communicate. Depending on how they work, APIs can be categorized into several types. Let’s learn about these API types in simple terms, with examples to make them easy to understand.

1. RESTful APIs

RESTful APIs are the most common type of APIs used in web development. They follow specific rules and use HTTP methods like:

• GET: To fetch data.
• POST: To create new data.
• PUT: To update existing data.
• DELETE: To remove data.

Example in .NET:

Here’s how you can create a RESTful API to fetch users:

[HttpGet]
[Route("api/users")]
public IActionResult GetUsers()
{
    var users = new List<string> { "Alice", "Bob", "Charlie" };
    return Ok(users);
}

This code fetches a list of users when you call the API.

2. SOAP APIs

SOAP (Simple Object Access Protocol) APIs are more structured and use XML for communication. These are commonly used in enterprise systems for secure communication, like payment processing.

Example in .NET:

To work with SOAP, you can use WCF (Windows Communication Foundation):

<binding name="BasicHttpBinding" />

.NET provides tools to generate SOAP clients for easier integration.

3. GraphQL APIs

GraphQL APIs are different because they let the client ask for exactly the data they need — no more, no less.

Example:

Imagine a .NET service using Hot Chocolate (a GraphQL library):

public class Query
{
    public User GetUser() => new User { Name = "Alice", Age = 25 };
}

You can request only the Name field:

query {
    getUser {
        name
    }
}

4. gRPC APIs

gRPC is a high-performance API that uses Protocol Buffers to transfer data. It is fast and ideal for real-time communication in systems like games or IoT devices.

Example in .NET:

Define a service in a .proto file:

service Greeter {
    rpc SayHello (HelloRequest) returns (HelloReply);
}

Implement it in .NET:

public override Task<HelloReply> SayHello(HelloRequest request, ServerCallContext context)
{
    return Task.FromResult(new HelloReply { Message = "Hello " + request.Name });
}

5. WebSocket APIs

WebSocket APIs allow two-way communication, meaning the server and client can send messages to each other. They are used in real-time applications like chat apps or stock price updates.

Example in .NET:

Enable WebSockets in your ASP.NET Core app:

app.UseWebSockets();

Handle WebSocket connections:

if (context.WebSockets.IsWebSocketRequest)
{
    var socket = await context.WebSockets.AcceptWebSocketAsync();
    // Handle communication
}

6. Streaming APIs

Streaming APIs provide a continuous flow of data. For example, they’re used in live updates like social media feeds or stock market data.

Example in .NET:

Use SignalR for real-time streaming:

public async Task SendMessage(string message)
{
    await Clients.All.SendAsync("ReceiveMessage", message);
}

This sends messages to all connected clients.

Conclusion

Each type of API serves different purposes. Whether you’re building simple web apps or high-performance systems, .NET makes it easy to work with these APIs.