Is it possible to mock local variable in a method

[garygao]

For example I have a method like this:

public class TaskService
{
    public List<Task> GetTasks(int contactId, DataContext dbContext)
    {
         ITaskRepository taskRepo = new TaskRepository(dbContext);
         List<Task> tasks = taskRepo.GetTasksFromDB(contactId).ToList();
         ......
         return tasks;
    }
}

How can I mock the local variable taskRepo when I writing test for method GetTasks?
I have test code like this:

public void GetTasksTest()
{
      var taskService = new Mock<TaskService>();
      var tasks = new List<Task> { new Task { Id = 111 } };
      // But how to mock the method `taskRepo.GetTasksFromDB(contactId).ToList()`?
      // And I don't want to pass taskRepo as a parameter.
}

[kzu]

If you can't write a manual mock that does it in plain C#, you can't with Moq.

This is one such case.