LINQ连接两个表并返回列表

Question

Update: In the comments it was made clear to me where I was getting confused, so although I can't mark a comment as an answer, this question has been solved. In reality everything was working fine when I used the ViewModel, I just wasn't using that properly in the view. Thanks for your help!

I'm building a site in MVC6. I'm trying to create a linq statement to join the booking and venue tables together, then return any bookings still forthcoming. I'm happy that my from and join statements are good, as well as my filter.

I have the following code:

private readonly ApplicationDbContext ctx;

public ForthcomingBookingsViewComponent(ApplicationDbContext c)
{
    ctx = c;
}

public IViewComponentResult Invoke(string filter)
{
    DateTime todaysDate = new DateTime();
    todaysDate = DateTime.Now;

    var res = (from p in ctx.Booking
               join i in ctx.Venue on p.VenueId equals i.VenueId
               where p.DonorId.Equals(filter)
               where p.BookingDate >= todaysDate
               select    )  //This is the line I'm struggling to work out
               .toList();
    return View(res);
}

The trouble comes in trying to get this in a list that I can refer to in my view. I've tried a couple of ways of doing this, first of all I tries to do the following:

select new { p.BookingDate, i.VenueName }

But the problem there is that I'm not sure how to refer to this as a model in my view.

I then thought I might use a ViewModel, so I could define what goes in it first:

   select new FCBViewModel { BookingDate = p.BookingDate, VenueName = i.VenueName })
   .ToList();

But once again I had trouble because this sets it as a single object rather than a list. To formalize the question:

How do I return a list of objects, from two joined tables, that I can use in my view?

Thanks!

Answer 1

You can do a projection in your LINQ expression using your view model class.

public IViewComponentResult Invoke(string filter)
{
    DateTime todaysDate = new DateTime();
    todaysDate = DateTime.Now;

    var fcbVmList = (from p in ctx.Booking
               join i in ctx.Venue on p.VenueId equals i.VenueId
               where p.DonorId.Equals(filter)
               where p.BookingDate >= todaysDate
               select new FCBViewModel { BookingDate = p.BookingDate,
                                         VenueName = i.VenueName })
               .toList();
    return View(fcbVmList);
}

In the above code, the variable fcbVmList will be a List of FCBViewModel and you are passing that to your view component's view. Now this list contains only one item or n items is depending on your where clause and your data in the tables. But it is returning a List. So make sure that your view is strongly typed to a collection of this class.

@model List<FCBViewModel>
<h2> @Model.Count() Bookings </h2>
@foreach(var item in Model)
{
  <p>@item.VenueName</p>
  <p>@item.BookingDate</p>
}

Answer 2

Did you try like this.

      var resultMBSSize = (from obj1 in objname.GetAll()
                           join obj2 in objname2.GetAll()
                           on obj1.id equals
                           obj2.id
                           where obj1.brandID== argumentvalue
                           select new objname
                           {
                           id=obj1.ModifierBrandSelectionSizeID,
                           name = obj2.Name,
                           price = obj1.Price,
                           address = obj2.address
                                         }).ToList()