python：列表操作(python: list manipulation)

 @LukasKabrt的评论指出了我正确的方向。 我没有直接比较Course对象，而是将现有的课程“暂时”转换为LINQ中的DTO并比较DTO。 现在我可以从coursesToDelete删除所有coursesToDelete 
 
var coursesToDelete = (
      from e in existing
      let dto = new CourseDto(e)
      where !incomingDtos.Contains(dto)
      select e).ToList();

The comment from @LukasKabrt pointed me in the right direction. Instead of comparing the Course objects directly, I convert the existing courses to DTOs "temporarily" inside the LINQ and compare DTOs. Now I am able to delete all from coursesToDelete
 
var coursesToDelete = (
      from e in existing
      let dto = new CourseDto(e)
      where !incomingDtos.Contains(dto)
      select e).ToList();