Below is a complete, clear, and real-time–friendly explanation of all important API types in C#, their definitions, how they work, and how to create each one with real-time examples.
In C#, APIs generally fall into 5 major categories:
SOAP API – WCF (Windows Communication Foundation)
REST API – ASP.NET Web API / ASP.NET Core API
gRPC API – High-performance contract-based API
Minimal API – Lightweight API in .NET 6+
GraphQL API – Query-based API
Below you will find:
✔ Definition
✔ When to use
✔ Real-time example
✔ How to create (steps + sample code)
1. SOAP API using WCF (Legacy – XML Based)
Definition
SOAP stands for Simple Object Access Protocol.
It uses XML for request and response and follows strict rules.
Use Case
Real-Time Example
Example: "Loan Status API" exposed by a bank to other systems.
How to Create WCF SOAP API in C#
Step 1: Create WCF Service Application
File → New → Project → WCF Service Application
IService1.cs
[ServiceContract]
public interface IService1
{
[OperationContract]
string GetLoanStatus(int loanId);
}
Service1.svc.cs
public class Service1 : IService1
{
public string GetLoanStatus(int loanId)
{
return "Status: Approved";
}
}
web.config
WCF exposes SOAP endpoints automatically.
2. REST API using ASP.NET Web API / ASP.NET Core API
Definition
REST (Representational State Transfer) uses:
It is the most commonly used API today.
Use Case
Real-Time Example
"E-commerce Order API", "Login API", "Product API".
How to Create REST API in ASP.NET Core
Step 1: Create Project
File → New → Project → ASP.NET Core Web API
Model
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
}
Controller
[ApiController]
[Route("api/[controller]")]
public class ProductController : ControllerBase
{
[HttpGet]
public IActionResult GetProducts()
{
return Ok(new List<string> { "Laptop", "Mobile" });
}
[HttpPost]
public IActionResult AddProduct(Product p)
{
return Ok("Product Inserted");
}
}
3. Minimal API (Introduced in .NET 6)
Definition
Minimal API is a super lightweight REST API created without controllers.
Use Case
✔ Microservices
✔ Small modules
✔ IoT devices
✔ Internal APIs
Real-Time Example
“Health Check API”
“Insert Logs API”
How to Create Minimal API
Program.cs
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
app.MapGet("/hello", () => "Hello World");
app.MapPost("/save", (Product p) => $"Saved {p.Name}");
app.Run();
Fastest way to expose endpoints.
4. gRPC API
Definition
gRPC is a high-performance, contract-first, binary communication protocol.
Uses Protocol Buffers (.proto) instead of JSON/XML.
Use Case
✔ High-speed internal microservices
✔ Real-time applications
✔ Banking & stock trading apps
✔ Communication between servers
Real-Time Example
"Stock price update service", "Chat service".
How to Create gRPC API in .NET Core
Step 1: Create Project
File → New → Project → gRPC Service
Proto File
protos/greet.proto
syntax = "proto3";
service Greeter {
rpc SayHello (HelloRequest) returns (HelloReply);
}
message HelloRequest {
string name = 1;
}
message HelloReply {
string message = 1;
}
C# Service
public class GreeterService : Greeter.GreeterBase
{
public override Task<HelloReply> SayHello(HelloRequest request, ServerCallContext context)
{
return Task.FromResult(new HelloReply
{
Message = "Hello " + request.Name
});
}
}
5. GraphQL API
Definition
GraphQL allows the client to ask exactly what data it needs (query based).
Unlike REST where server decides the shape.
Use Case
Real-Time Example
Facebook uses GraphQL for retrieving user feeds.
How to Create GraphQL API in C#
Install Package
HotChocolate.AspNetCore
Query.cs
public class Query
{
public string Hello() => "Hello GraphQL";
}
Program.cs
builder.Services.AddGraphQLServer()
.AddQueryType<Query>();
app.MapGraphQL();
Comparison of API Types
| API Type | Format | Speed | Security | Best For |
|---|
| SOAP (WCF) | XML | Medium | Very High | Banking, govt |
| REST API | JSON | Fast | Medium | Web, mobile, ecommerce |
| Minimal API | JSON | Very Fast | Medium | Microservices |
| gRPC | ProtoBuf | Extremely Fast | High | Internal microservices |
| GraphQL | JSON | Fast | Medium | Complex data apps |