LINQ query to include the parent name in the child item - linq

Question

public class Order
{
public int OrderId { get; set; }
public DateTime OrderDate { get; set; }
public bool MarkAsPresent { get; set; }
public List<OrderItem> OrderItems { get; set; }
}
public class OrderItem
{
public int OrderItemId { get; set; }
public int OrderId { get; set; }
public int ProductId { get; set; }
public int Quantity { get; set; }
public decimal Price { get; set; }
public Order Order { get; set; }
public Product Product { get; set; }
}
public class Product
{
public int ProductId { get; set; }
public string ProductName { get; set; }
}
Please someone can help? From ASP.NET Core API controller, I need to return the following JSON. Please note that in the OrderItems, it includes the Product.ProductName. Also, if the Order.MarkAsPresent is true, then the productName should be replaced as 'Gift' in the JSON data.
{
"order": {
"orderId": "123",
"orderDate": "01-May-2021",
"orderItems": [
{ "productName": "Pen", "quantity": "25", "retailPrice": "3.50" },
{ "productName": "Paper", "quantity": "500", "retailPrice": "5.50" },
]
}
}

Answer 1

The two answers given so far are far too cumbersome. There's a very common, standard way to do this:
var result = from o in context.Order
select new
{
o.OrderId,
o.OrderDate,
OrderItems =
from oi in o.OrderItems
select new
{
ProductName = o.MarkAsPresent
? "Gift"
: oi.Product.ProductName,
oi.Quantity,
RetailPrice = oi.Price
}
};
You didn't define RetailPrice, so I assume it's just OrderItem.Price. If you like, the two select new statement can be replaced by projections into named DTO classes like OrderDto and OrderItemDto, respectively.

Answer 2

You can do it using an OrderDto.
public class OrderDto
{
public int OrderId { get; set; }
public DateTime OrderDate { get; set; }
public object OrderItems { get; set; }
public OrderDto(int orderId, DateTime orderDate)
{
OrderId = orderId;
OrderDate = orderDate;
}
}//Cls
//--------------------------------------------//
public class OrderItemDto
{
public string ProductName { get; set; }
public int Quantity { get; set; }
public decimal RetailPrice { get; set; }
public OrderItemDto(string giftName, int quantity, decimal retailPrice)
{
ProductName = giftName;
Quantity = quantity;
RetailPrice = retailPrice;
}
}//Cls
//--------------------------------------------//
public class GiftDto
{
public string GiftName { get; set; }
public int Quantity { get; set; }
public decimal RetailPrice { get; set; }
public GiftDto(string giftName, int quantity, decimal retailPrice)
{
GiftName = giftName;
Quantity = quantity;
RetailPrice = retailPrice;
}
}//Cls
Add this method to your Order class
public class Order
{
public int OrderId { get; set; }
public DateTime OrderDate { get; set; }
public bool MarkAsPresent { get; set; }
public List<OrderItem> OrderItems { get; set; }
public OrderDto ToDto()
{
var dto = new OrderDto(OrderId, OrderDate);
if (MarkAsPresent)
dto.OrderItems = OrderItems.Select(oi => new GiftDto(oi.Product.ProductName, oi.Quantity, oi.Price));
else
dto.OrderItems = OrderItems.Select(oi => new OrderItemDto(oi.Product.ProductName, oi.Quantity, oi.Price));
return dto;
}
}//Cls
Then in your action return something like Ok(order.ToDto());
Examples:
[HttpGet]
[AllowAnonymous]
public IActionResult OrderGift()
{
var order = new Order()
{
OrderId = 1,
OrderDate = DateTime.Now,
MarkAsPresent = true
};
order.OrderItems = new List<OrderItem>();
for (int i = 0; i < 5; i++)
{
order.OrderItems.Add(
new OrderItem()
{
Order = order,
OrderId = order.OrderId,
OrderItemId = i + 10,
Price = (i + 1) * 10,
Product = new Product()
{
ProductId = i + 20,
ProductName = $"Name {i}"
},
ProductId = i + 20,
Quantity = i * 2 + 4
});
}//for
return Ok(order.ToDto());
}///OrderGift
[HttpGet]
[AllowAnonymous]
public IActionResult OrderRegular()
{
var order = new Order()
{
OrderId = 1,
OrderDate = DateTime.Now,
MarkAsPresent = false
};
order.OrderItems = new List<OrderItem>();
for (int i = 0; i < 5; i++)
{
order.OrderItems.Add(
new OrderItem()
{
Order = order,
OrderId = order.OrderId,
OrderItemId = i + 10,
Price = (i + 1) * 10,
Product = new Product()
{
ProductId = i + 20,
ProductName = $"Name {i}"
},
ProductId = i + 20,
Quantity = i * 2 + 4
});
}//for
return Ok(order.ToDto());
}//OrderRegular

Answer 3

You can also use the Linq's let clause:
var report =
from o in orders
let orderItems =
from oi in o.OrderItems
select new {
productName = o.MarkAsPresent ? "Gift" : oi.Product.ProductName,
quantity = oi.Quantity,
retailPrice = oi.Price
}
select new {
orderId = o.OrderId,
orderDate = o.OrderDate,
orderItems
};

Answer 4

Use join to join the two models so we can connect every properties, and group all the
data by
OrderId and OrderDate, then just select the property you want to show.
About the gift,you can use if else in select.
Following is my demo:
[HttpGet]
public JsonResult Get()
{
var model = (from e in _context.OrderItems.Include(x=>x.Order).ToList()
join y in _context.Products.ToList() on e.OrderItemId equals y.ProductId
group new { e, y } by new { e.OrderId, e.Order.OrderDate } into g
select new
{
order = new
{
orderId = g.Key.OrderId,
orderDate = g.Key.OrderDate,
orderItems = (
from t in g.ToList()
select new
{
productName = t.e.Order.MarkAsPresent == true ? "Gift" : t.y.ProductName,
quantity = t.e.Quantity,
retailPrice = t.e.Price
}
).ToList()
}
}).ToList();
return new JsonResult(model);
}
Result: