I have a list of int called "motor_list" = 2, 3, 5, 3, 8, 5, 5, 9, 8 (List 2)
(3 = 2 times in the list)
(5 = 3 times)
I have a table (Item), which content row "ItemId, Name, Date, Location", and it's only content 2 datas :
(ItemId) = 3 and 5. (List 1)
var data = _context.Item.Where(x => motor_list.Contains(x.ItemId));
Using the above code, I'm only getting two data which is obviously right technically,
now I want to get data but according to the occurrence of motor_list (List 2), and no the one for Item table.
I mean I want to get something like :
ItemId 3 should pull 2 times the same data, and
ItemId 5 should pull 3 times.
Try this code
List<int> list1 = new List<int>() { 3, 5 };
List<int> list2 = new List<int>() { 2, 3, 5, 3, 8, 5, 5, 9, 8 };
var data = list2.GroupBy(x => x).Where(a => list1.Contains(a.Key));
var result= data.Select(g => $"ItemId {g.Key} should pull {g.Count()} times").ToList();
foreach (var item in result)
{
Console.WriteLine(item);
}
Use join to return exactly the items in the motor_list.
var data = motor_list
.Join(_context.Item,
left => left,
right => right.ItemId,
(left, right) => new { items = right });
or a little further away
var data = _context.Item.ToList();
var result = lst.Select(x => new
{
item = data.Where(a => a.ID == x).FirstOrDefault()
}).Where(a=>a.item != null).ToList();
I'm not sure what you mean by "ItemId 3 should pull 2 times the same data". It sounds like you either want the count of each ItemId in motor_list, or you want the duplicate items returned in the results.
Here's how you can accomplish either:
class Item
{
public int ItemId { get; set; }
}
static void Main(string[] args)
{
List<Item> contextItems = new List<Item> { new Item { ItemId = 3 }, new Item { ItemId = 5 } };
var motor_list = new List<int> { 2, 3, 5, 3, 8, 5, 5, 9, 8 };
// To get the count of each contextItem in motor_list:
var itemCount = contextItems
.Select(contextItem =>
motor_list.Count(motorId => motorId == contextItem.ItemId))
.ToList();
// result: { 2, 3 }
// To get duplicate items for each contextItem in motor_list
var items = motor_list
.Where(motorId =>
contextItems.Any(contextItem => contextItem.ItemId == motorId))
.ToList();
// result: { 3, 5, 3, 5, 5 }
}