C＃LINQ OrderBy on nullable->始终在列表末尾设置空值

如何解决C＃LINQ OrderBy on nullable->始终在列表末尾设置空值

是否有一种简单的方法，可以通过升序对可空值列表进行排序，并将空值放在列表末尾？就像一个选项之类的

如果没有，那么哪种方法最好：

1. 编写我自己的排序lambda

   import Foundation
   import UIKit
   
   class MemberProfilePhotosViewController: UIPageViewController {
       
       private let profilePhotoURLs: [URL]
       private let profilePhotoViewControllers: [MemberProfilePhotoViewController]
       private var pageControl: UIPageControl?
       
       // MARK: - Initialization
       
       init(profilePhotoURLs: [URL]) {
           self.profilePhotoURLs = profilePhotoURLs
           profilePhotoViewControllers = profilePhotoURLs.map { (profilePhotoURL) -> MemberProfilePhotoViewController in
               MemberProfilePhotoViewController(profilePhotoURL: profilePhotoURL)
           }
           super.init(transitionStyle: .scroll,navigationOrientation: .horizontal,options: nil)
       }
       
       required init?(coder: NSCoder) {
           fatalError()
       }
       
       // MARK: UIViewController
       
       override func loadView() {
           super.loadView()
           pageControl = UIPageControl(frame: CGRect.zero)
           pageControl!.numberOfPages = profilePhotoViewControllers.count
           self.view.addSubview(pageControl!)
       }
       
       override func viewDidLoad() {
           super.viewDidLoad()
           dataSource = self
           delegate = self
           if let firstViewController = profilePhotoViewControllers.first {
               setViewControllers([firstViewController],direction: .forward,animated: true,completion: nil)
           }
       }
       
       override func viewWillLayoutSubviews() {
           super.viewWillLayoutSubviews()
           if let pageControl = pageControl {
               let pageControlSize = pageControl.size(forNumberOfPages: profilePhotoViewControllers.count)
               pageControl.frame = CGRect(
                   origin: CGPoint(x: view.frame.midX - pageControlSize.width / 2,y: view.frame.maxY - pageControlSize.height),size: pageControlSize
               )
           }
       }
       
       // MARK: Private Helpers
       
       private func indexOf(_ viewController: UIViewController) -> Int? {
           return profilePhotoViewControllers.firstIndex(of: viewController as! MemberProfilePhotoViewController)
       }
   }
   
   extension MemberProfilePhotosViewController: UIPageViewControllerDelegate {
       func pageViewController(_ pageViewController: UIPageViewController,didFinishAnimating finished: Bool,previousViewControllers: [UIViewController],transitionCompleted completed: Bool) {
           guard let selectedViewController = pageViewController.viewControllers?.first else { return }
           if let indexOfSelectViewController = indexOf(selectedViewController) {
               pageControl?.currentPage = indexOfSelectViewController
           }
       }
   }
   
   extension MemberProfilePhotosViewController: UIPageViewControllerDataSource {
       func pageViewController(_ pageViewController: UIPageViewController,viewControllerBefore viewController: UIViewController) -> UIViewController? {
           guard let viewControllerIndex = profilePhotoViewControllers.firstIndex(of: viewController as! MemberProfilePhotoViewController) else {
               return nil
           }
           let previousIndex = viewControllerIndex - 1
           guard previousIndex >= 0 else {
               return nil
           }
           guard profilePhotoViewControllers.count > previousIndex else {
               return nil
           }
           return profilePhotoViewControllers[previousIndex]
       }
       
       func pageViewController(_ pageViewController: UIPageViewController,viewControllerAfter viewController: UIViewController) -> UIViewController? {
           guard let viewControllerIndex = profilePhotoViewControllers.firstIndex(of: viewController as! MemberProfilePhotoViewController) else {
               return nil
           }
           let nextIndex = viewControllerIndex + 1
           let profilePhotoViewControllersCount = profilePhotoViewControllers.count
           guard profilePhotoViewControllersCount != nextIndex else {
               return nil
           }
           guard profilePhotoViewControllersCount > nextIndex else {
               return nil
           }
           
           return profilePhotoViewControllers[nextIndex]
       }
   }
   
   

2. 仅对非null值进行排序，并在其后添加null值

   list.Sort((v1,v2) => 
   {
      if (v1.HasValue && v2.HasValue) return v1.CommpareTo(v2);
      else if (!v1.HasValue) return -1;
      else if (!v2.HasValue) return 1;
      else return 0;
   })