Azure Functions v2 and above can include a Startup class, which enables the use of .NET Core's built-in Dependency Injection (DI). This allows for better project architecture, testing, and maintainability. To add DI to an Azure Function, a new file called "Startup.cs" is added with a namespace equal to the name of the project. The class implements FunctionsStartup, which itself implements IWebJobStartup. Dependencies are registered in the IoC container using services such as AddSingleton, AddScoped, and AddTransient. Injected classes can be used in HTTP Trigger functions by adding them as private properties with constructor injection. This enables better maintainability and testability of Azure Function projects.