SelectListItem未设置所选值

Question

I have these classes.

public class Store {
  // constructor
  public int Id { get; set; }
  public string Name { get; set; }

  public virtual ICollection<Stock> Stocks { get; set; }
}

public class Stock {
  public int Id { get; set; }
  public int StoreId { get; set; }
  public int ProductId { get; set; }

  public virtual Store Store { get; set; }
  public virtual Product Product { get; set; }
}

public class Product {
  // constructor
  public int Id { get; set; }
  public string Name { get; set; }

  public ICollection<Stock> Stocks { get; set; }
}

public class Order {
  // constructor
  public int Id { get; set; }

  public virtual ICollection<OrderItem> OrderItems { get; set; }
}

public class OrderItem {
  public int Id { get; set; }

  public ICollection<Store> Stores { get; set; }
  public Item Item { get; set; }
  public Order Order { get; set; }
}

Fluid api:

public class OrderItemMap : EntityTypeConfiguration<OrderItem> {
  public OrderItemMap() {
    HasMany(i => i.Stores)
      .WithMany()
      .Map(m => {
          m.MapLeftKey("OrderItemId");
          m.MapRightKey("StoreId");
          m.ToTable("FromStore");
        });
  }
}

Now, for instance I have created an order and set my details and also the item's store as to where they should get the item to deliver it. Note: An item can have many stores .

My problem is.. If the user wants to Edit the order. I don't know how to display the list of stores as dropdown and it's selected value.

Here's what I have done so far:

var order = _db.Orders.Find(orderId);
var orderVm = new EditOrderVm {
  OrderId = order.Id,
  OrderItems = order
               .OrderItems
               .Select(o => new EditOrderItemVm {
                 OrderItemId = o.Id,
                 OrderId = o.OrderId,
                 ProductId = o.ProductId,
                 Stores = (from sc in o.Product.Stocks
                           from st in o.Stores.DefaultIfEmpty()
                           select new {
                             Id = sc.Store.Id,
                             Name = sc.Store.Name
                           }).ToSelectList(s => s.Name, s => s.Id, s => true)
               })
}

My VM:

public class EditOrderItemVm {
  // removed some for brevity
  public IEnumerable<SelectListItem> Storses { get; set; }
}

My helper (ain't mine)

public static IEnumerable<SelectListItem> ToSelectList<T, TTextProperty, TValueProperty>(this IEnumerable<T> instance, Func<T, TTextProperty> text, Func<T, TValueProperty> value, Func<T, bool> selectedItem = null)
        {
            return instance.Select(t => new SelectListItem
            {
                Text = Convert.ToString(text(t)),
                Value = Convert.ToString(value(t)),
                Selected = selectedItem != null && selectedItem(t)
            });
        }

My View:

@Model.OrderNumber
@foreach(var item in Model.OrderItems) {

    @Html.DropDownListFor(model => item.StoreId, item.Stores, "Select store")
    @Html.ValidationMessageFor(model => item.StoreId)
}

With the query above, I can populate the dropdown with the list of stores as to where the product is stored but i don't know how to set of what was selected during creation of order.

It would be great if I can populate the dropdown with the list of stores as to where the item is stored and also set it's selected value.

Answer 1

This line should look like this, You have to take all your stores from db and select those who are involved in current order.

var order = _db.Orders.Find(orderId);
var stores = _db.Stores; // take all stores from DB
var orderVm = new EditOrderVm {
  OrderId = order.Id,
  OrderItems = order
               .OrderItems
               .Select(o => new EditOrderItemVm {
                 OrderItemId = o.Id,
                 OrderId = o.OrderId,
                 ProductId = o.ProductId,
                 Stores = (from st in stores // all stores
                           select new {
                             Id = st.Id,
                             Name = st.Name
                        }).ToSelectList(
                            s => s.Name,
                            s => s.Id, 
                            s => o.Stores.Any(sto => sto.Id == s.Id) //select only existing stores
                        )

               })
}

Answer 2

您必须像s => s.Id == YOUR_CURRENT_STORE_Id一样来代替s => true 。