Introduction

In today's software development world, it's super important to keep things up-to-date while adding new features. One of the most important steps in this process is using APIs and managing their versions. In this article, we'll walk you through the steps of how to use API versioning with .NET Core to make sure your users and clients have a smooth transition.

What is API versioning?

Versioning assigns unique identifiers to different versions of your application programming interface (API). This enables you to make changes to your API or introduce breaking changes without affecting existing clients. Version management allows new and existing clients to continue to use your API while providing a roadmap for your development team.

Implementing API Versioning in .NET Core

Let's dive into the steps required to implement API versioning in your .NET Core application:

 Step 1: Create a .NET Core Web API Project

If you don't have a .NET Core Web API project yet, create one using your preferred development environment.

 Step 2: Install the Microsoft.AspNetCore.Mvc.Versioning NuGet Package

To enable API versioning, you'll need to install the `Microsoft.AspNetCore.Mvc.Versioning` package. You can do this via the NuGet Package Manager or by adding it to your project's `.csproj` file.

PM> install Microsoft.AspNetCore.Mvc.Versioning

 Step 3: Configure API Versioning in Startup.cs

In your `Startup.cs` file, configure API versioning in the `ConfigureServices` method:

services.AddApiVersioning(options => {    
options.ReportApiVersions = true;    
options.AssumeDefaultVersionWhenUnspecified = true;    
options.DefaultApiVersion = new ApiVersion(1, 0); 
});

1. ReportApiVersions enables API version information in the response headers.
2. AssumeDefaultVersionWhenUnspecified specifies whether to assume the default version when none is specified.
3. DefaultApiVersion sets the default version for your API.

 Step 4: Attribute-Based Versioning

In .NET Core, you can apply versioning at the controller or action level using attributes. For example:

[ApiVersion("1.0")] 
[Route("api/v{version:apiVersion}/[controller]")] 
public class ValuesController : ControllerBase {    
// Controller actions here 
}

In this example, the `ValuesController` is versioned using the `[ApiVersion]` attribute.

 Step 5: Versioning by URL

You can also version your API using URLs:

app.UseEndpoints(endpoints => {    
	endpoints.MapControllers().WithMetadata(new    
	{        
	Version = "2.0"    
	}).RequireAuthorization(); 
});

 Step 6: Versioning by Query Parameter

If you prefer versioning via query parameters, you can configure it like this:

services.AddApiVersioning(options => {    
options.ApiVersionReader = new QueryStringApiVersionReader("version");    options.AssumeDefaultVersionWhenUnspecified = true;    
options.DefaultApiVersion = new ApiVersion(1, 0); 
});

In this case, the API version is specified as a query parameter, e.g., `/api/values?version=1.0`.

Version Management and Deprecation

One of the most effective ways to manage API versions is with a deprecation strategy. When an API version expires, clients need to know about it and be able to quickly migrate to a new version. This allows users to adapt to changes without any problems.

 Conclusion

API versioning has long been recognized as one of the best practices for the.NET Core development community. It allows you to update your APIs while maintaining backward compatibility, which enhances the overall developer and user experience.

Most of us have heard about API versioning at some point, and have implemented it into our.NET Core applications. If you haven’t done it yet, you might be wondering what you need to do.