如何在c#中将字符串转换为LiteDb.ObjectId，反之亦然

public class TaskModel
{
   [BsonId]
   public ObjectId Id { get; set; }
   public string Name { get; set; }
}
public class TaskViewModel
{
   public string Id { get; set; }
   public string Name { get; set; }
}
public class AutoMapperProfile : Profile
{
    public AutoMapperProfile()
    {
        CreateMap<TaskViewModel, TaskModel>()
            .ForMember(dest=>dest.Id,opt=>opt.MapFrom(src=>src.Id));
        CreateMap<TaskModel,TaskViewModel>()
            .ForMember(dest=>dest.Id,opt=>opt.MapFrom(src=>src.Id));
    }  
}
[Route("api/[controller]/[action]")]
[ApiController]
public class TaskController : ControllerBase
{
    // POST: api/Task/Post
    [HttpPost]
    public IActionResult Post([FromForm] TaskViewModel taskViewModel)
    {
        taskModel.Id = taskViewModel.Id;        //ERROR: Connot implicitly convert 'string' to 'LiteDB.ObjectId'
        taskModel.Name = taskViewModel.name
    }   
}

我有 LiteDB.ObjectId = 602f9484a5a84e0bc31938a8，所以我需要将 LiteDB.ObjectId 转换为字符串并使用 cersa。在此先感谢您的帮助。