The problem interface for the Responsive Autosave Problem (lookup the post on blogger)

IAsyncSaveService.cs

// Instances of this class are not thread-safe
// E.g. only one thread can safely call Save and DisposeAsync
//
interface IAsyncSaveService {
  // this function schedules save operation to be performed
  // implementers of this interface must ensure, that only one save operation can run at the same time
  // saveOperation is considered completed when the task it returned is completed
  void Save(Func<Task> saveOperation);
  // after a call to this function no calls to Save are allowed and must throw ObjectDisposedException
  // this function can be called any number of times
  // awaiting the task, returned by this function must ensure, that the last save operation added by Save() is completed
  Task DisposeAsync();
}