In C#, there are several methods that can be used to implement multi-threading.

1. By using the Thread class, you can create a Thread object, pass the method you want to execute as a parameter to the constructor of Thread, and then call the Start method to start the thread.
2. By using the ThreadPool class, you can add a delegate method to the thread pool for execution with the ThreadPool.QueueUserWorkItem method.
3. By using the Task class, you can create a task and submit it to the thread pool for execution using the Task.Run method.
4. Using the Parallel class: you can use static methods of the Parallel class such as Parallel.Invoke, Parallel.For, Parallel.ForEach, etc. to execute tasks in parallel.
5. By utilizing asynchronous methods and the await keyword, you can add the async keyword before a method and then use the await keyword within the method to wait for the completion of asynchronous operations.
6. Using the Task Parallel Library (TPL): The TPL provides a set of classes and methods for parallel programming, making it easy to implement multi-threading tasks.

These methods can all achieve multithreading, and the appropriate method can be chosen based on the specific scenario and requirements.