显示记录外键的标题

Question

Good day! Faced a problem, there is a table,4 fields (Id,Parent Id,Title,Created, Description) where Parent Id is the foreign key to the Id in the same table. How on the client side to display in the table is not ParentId namely the parent record Title, if any?

Class:

public class MyClass
    {
        public int Id { get; set; }
        public int? ParentId { get; set; }
        public string Title { get; set; }
        public DateTime Created { get; set; }
        public string Description { get; set; }
    }

Controller:

        public ViewResult Index(string sortOrder, string currentFilter, string searchString, int? page)
        {

            Repository repository = new Repository();

            ViewBag.CurrentSort = sortOrder;

            ViewBag.NameSortParm = String.IsNullOrEmpty(sortOrder) ? "Name desc" : "";
            ViewBag.DateSortParm = sortOrder == "Date" ? "Date desc" : "Date";

            if (Request.HttpMethod == "GET")
            {
                searchString = currentFilter;
            }
            else
            {
                page = 1;
            }
            ViewBag.CurrentFilter = searchString;

            var records = from s in repository.GetMyClass()  select s;

            if (!String.IsNullOrEmpty(searchString))
            {
                records = records.Where(s => s.Title.ToUpper().Contains(searchString.ToUpper()));
            }



            switch (sortOrder)
            {
                case "Name desc":
                    records = records.OrderByDescending(s => s.Title);
                    break;
                case "Date":
                    records = records.OrderBy(s => s.Created);
                    break;
                case "Date desc":
                    records = records.OrderByDescending(s => s.Created);
                    break;
                default:
                    records = records.OrderBy(s => s.Title);
                    break;
            }

            int pageSize = 4;
            int pageIndex = (page ?? 1);



            return View("_TableRecords",records.ToPagedList(pageIndex, pageSize));
        }

Answer 1

You need to implement a Self Join.

First you need to add one more field to your ViewModel:

public string ParentTitle { get; set; }

And then change the way you get your data, it should be something like that:

IEnumerable<MyClass> myData = 
    from m in t.YourEntity
    join e1 in t.YourEntity on m.ParentId equals e1.Id
    select new MyClass
    { 
        Id = m.Id,
        ParentId = m.ParentId,
        Title = m.Title,
        ParentTitle = e1.Title,
        Created = m.Created,
        Description = m.Description
    };

    return View(myData.ToList());

Answer 2

Try this, selecting all data including parent title in your sql script, like this:

DECLARE @DemoTable TABLE(
Id INT,
ParentId INT,
Title NVARCHAR(50),
Created DATETIME,
Description NVARCHAR(50))

INSERT INTO @DemoTable VALUES(1, NULL, 'Fruit', '2018-03-06 17:00:00.000', '')
INSERT INTO @DemoTable VALUES(2, 1, 'Apple', '2018-03-06 17:00:00.000', '')
INSERT INTO @DemoTable VALUES(3, 1, 'Banana', '2018-03-06 17:00:00.000', '')
INSERT INTO @DemoTable VALUES(4, NULL, 'Sport', '2018-03-06 17:00:00.000', '')
INSERT INTO @DemoTable VALUES(5, 4, 'Baseball', '2018-03-06 17:00:00.000', '')
INSERT INTO @DemoTable VALUES(6, 4, 'Football', '2018-03-06 17:00:00.000', '')


SELECT T1.Id, T1.Title, T1.ParentId, T2.Title AS 'ParentTitle'
FROM @DemoTable AS T1
LEFT JOIN @DemoTable AS T2
ON T1.ParentId = T2.Id

Result of execution

You can get all data including parent title
And then, change your viewmodel to this:

public class MyClass
    {
        public int Id { get; set; }
        public int? ParentId { get; set; }
        public string ParentTitle { get; set; }
        public string Title { get; set; }
        public DateTime Created { get; set; }
        public string Description { get; set; }
    }