Plus I'd recommend against doing these in a view. Ideally for separation of logic and the view these should be done in a controller and passed in to a viewmodel to the view.

Do you have a sample code on how to use CategoryRepository?

- Category on the block is s CategoryList which is a list of IDs.
- Inject instance of CategoryRepository
- Call the get method on the CategoryRepository instance passing in one of the IDs from the CategoryList

It's fairly straight forward. https://world.optimizely.com/csclasslibraries/cms/EPiServer.DataAbstraction.CategoryRepository?version=8

But what do you mean by “inject instance”?

If you're not sure what dependency injection is I'd google it and have a read. It's a core part of modern application design within the .NET and C# platform. Optimizely is built from the ground up to be able to inject dependencies (usually by constructor) so you NEED to understand it to work with the platform.

Read this after you've read about DI in .NET https://world.optimizely.com/documentation/developer-guides/CMS/initialization/dependency-injection/

However as mentioned you should be doing this in a Controller or services run within a controller. The standard way is to inject the instance in the constructor of your controller for your block as you can't inject things in views as they are just for presentation. You can use the ServiceLocator with code such as ServiceLocator.Current.GetInstance however it's an anti pattern and shouldn't be used in a view