Steps to localize your ASP.NET Core app

I didn't find it obvious how to set up .NET localization in ASP.NET Core, so here is a quick list of what you have to set up to help you. The information is already out there, so this is a list of links to Microsoft documentation.

1. Configure localization which sets up the localization services and the name of the folder that holds the resource files (see step 3 later).
2. Configure middleware which sets up what cultures you want to support, and ways to get the user's culture.
3. Create a new class, or use an existing class (e.g. HomeController) to define part of the resource files’ name - I refer to this class as TResource. These TResource classes must be in the ASP.NET Core project.
4. Add the resource files you need where each resource file that has a filename of {typeof(TResource).{culture name of entries}.resx

I found the Microsoft document didn't have nice step-by-step section on how to setup localization in an ASP.NET Core app, here are some other articles that you might find useful:

• Building Multilingual Applications in ASP.NET Core – excellent step-by-step article
• Localization in ASP.NET Core Web API – another excellent step-by-step article (.NET 6)
• ASP.NET Core Localization Deep Dive – shows all the different localization parts

NOTE: If you are using the DefaultLocalizer and SimpleLocalizer for all the localization, then you won't need a resource file for the defaultCulture messages, as the strings / FormattableStrings used in these services already have the correct message.

If you want examples of adding localization to an ASP.NET Core app, then have a look at:

• The Startup in Microsoft's example code. Note this old, (netcoreapp2.1) but localization haven't changed.
• The Program in my .NET 6 example in the Net.LocalizeMessagesAndErrors repo. This uses the culture of the request to show English or French/
• The Program in Example1 app in the AuthP repro. This uses a cookie to set the culture. You can select between English (default) and French.
• Other example code in the listed articles.