Task Canvas lets you edit multiple methods from different classes in one window in Visual Studio 2015/2017. It significantly reduces tab switching and jumping from place to place within a file:
Task Canvas interface is task-focused to reduce information overload and make multitasking easy. All currently open document tabs and code blocks are automatically saved in the current task context. It is most useful when you have repeatable periodic tasks or work on several tasks in parallel. To start working on a task just select it from the list:
Visit the Task Canvas home page for more information.