ASP.NET Core – default API version with url path versioning

1. Introduction.

When you start versioning your API sometimes you want to have access to your endpoints without specifying version explicitly. Thanks to Microsoft.AspNetCore.Mvc.Versioning library this can be easily achieved with proper setup of configuration action. However, it turns out that in order to enable default API version for url path versioning, there are a couple additional steps to do.

2. Default API version without url path versioning

Let’s start with the initial setup of API versioning which will work for every type of versioning apart from url path versioning. All you have to do is to assign an ApiVersionSelector and set the AssumeDefaultVersionWhenUnspecified property to true.

Now when the user will try to access the endpoint without specifying version explicitly the ApiVersionSelector will select proper version – in this case highest available version.

3. Default Api version with URL path versioning

Running the same configuration against controllers which are versioned via url path (not query string)

will result with 404 status code, as routing is not able to match the url.
Fortunately, unlike the ASP.NET Web API, ASP.NET Core allows us to have multiple route attributes applied to given controller, so in order to fix the issue we just have to add

attribute to versioned controllers. From now on we can access our API without specifying version as well as with version specified.

4. Adding default route with convention

If you don’t want to specify default route manually for every controller, you can do it via application model convention. The interesting thing about it is the fact that apart from changing existing values of application model we can also add new items to it. This means that we can add additional SelectorModel with our default route to Selectors’ collection

Now we can get rid of [Route(“[controller]”)] attribute from our versioned controllers and just rely on convention which can be added as follows

Source code for this post can be found here

ASP.NET Core – default API version with url path versioning