Question

我想知道如何重构这样的一段代码。这是控制器中的一种方法，我正在通过ViewBag将2个SelectList传递给HTML。

public async Task<IActionResult> Index()
{
    var teacherInfo =  context.Teachers.OrderBy(x => x.Id);
    IEnumerable<SelectListItem> selectList = from s in teacherInfo
                                             select new SelectListItem
                                             {
                                                 Value = s.Id.ToString(),
                                                 Text = s.FirstName + " " + s.LastName.ToString()
                                             };
    ViewBag.TeacherId = new SelectList(selectList, "Value", "Text");

    var studentInfo = context.Students.OrderBy(x => x.Id);
    IEnumerable<SelectListItem> selectListStudents = from s in studentInfo
                                             select new SelectListItem
                                             {
                                                 Value = s.Id.ToString(),
                                                 Text = s.FirstName + " " + s.LastName.ToString()
                                             };
    ViewBag.StudentId = new SelectList(selectListStudents, "Value", "Text");


    return View();

}

我已经尝试过了，但是似乎我不能使用这样的泛型，因为T没有为Id和其他字段定义：

private async Task<IEnumerable<SelectListItem>> GetSelectListItem<T>(IOrderedQueryable<T> dbData)
{
    IEnumerable<SelectListItem> selectList = from s in dbData 
                                             select new SelectListItem
                                             {
                                                 Value = s.Id.ToString(),
                                                 Text = s.FirstName + " " + s.LastName.ToString()
                                             };
    return selectList;
}

任何帮助将不胜感激

Answer 1

您需要将T约束到包含这些属性的接口上

internal interface IListItem
{
    int Id { get; }
    string FirstName { get; }
    string LastName { get; }
}

然后让您的学生和老师实现此界面。

Answer 2

您可以创建一个通用类，供学生和教师类继承。

public class BaseClassForSelectItems
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

 public class Students: BaseClassForSelectItems
{ 
}

  public class Teachers: BaseClassForSelectItems
{ 
}

public async Task<IActionResult> Index()
    {
        var teacherInfo = context.Teachers.OrderBy(x => x.Id);
        IEnumerable<SelectListItem> selectList = await GetSelectListItem(teacherInfo);
        ViewBag.TeacherId = new SelectList(selectList, "Value", "Text");
        var studentInfo = context.Students.OrderBy(x => x.Id);
        IEnumerable<SelectListItem> selectListStudents = await GetSelectListItem(studentInfo);
        ViewBag.StudentId = new SelectList(selectListStudents, "Value", "Text");
        return View();
}


    private async Task<IEnumerable<SelectListItem>> GetSelectListItem<T>(IOrderedQueryable<T> dbData) where T : BaseClassForSelectItems
    {
        IEnumerable<SelectListItem> selectList = from s in dbData
                                                 select new SelectListItem
                                                 {
                                                     Value = s.Id.ToString(),
                                                     Text = s.FirstName + " " + s.LastName.ToString()
                                                 };
        return selectList;
    }

如何重构这些？

2 个答案: