linq query to display data

Question

linq query to display data

djnilo dj 6

hello good afternoon programmers I have an order application made visual studio 2015 entity c# linq
I am in the printing part, make a query to show the data, this query is wrong

an order containing

product name quantity
french fries girls 1
chicken boy 1
french fries girls 1

when making the query it brings me

report = printlist.GroupBy(x => x.ProductId).Select(group => group.First()).ToList();

I get this output is wrong

product name quantity
french fries girls 1
chicken boy 1

public static void PrintReceipt(BOX box, List

P a u l 10,761 Reputation points

2022-12-15T18:39:40.493+00:00
Just to clarify: you have 3 items in your receipt but 2 of the items are for the same product (i.e. french fries girls)?

If you don't want to group the quantities of items relating to the same product then do you even need the .GroupBy()?

If you did want to group then I'd imagine you could change this bit:

.Select(group => group.First())

To something like:

.Select(group => new { Product = group.First().ProductName, Quantity = group.Sum(i => i.Quantity) })
djnilo dj 6 Reputation points

2022-12-16T19:15:09.107+00:00

Thank you very much for answering but I get this error

1 answer

Your answer

P a u l 10,761 Reputation points

2022-12-15T18:39:40.493+00:00

Just to clarify: you have 3 items in your receipt but 2 of the items are for the same product (i.e. french fries girls)?

If you don't want to group the quantities of items relating to the same product then do you even need the .GroupBy()?

If you did want to group then I'd imagine you could change this bit:

.Select(group => group.First())

To something like:

.Select(group => new { Product = group.First().ProductName, Quantity = group.Sum(i => i.Quantity) })
djnilo dj 6 Reputation points

2022-12-16T19:15:09.107+00:00

Thank you very much for answering but I get this error

Answer 1

Michael Taylor 60,161

The GroupBy groups all rows together that have the same key. In your case you're grouping by ProductId therefore all entities that have the same ProductId are grouped together. From this group you are then grabbing just the first product from that group so you're basically just getting the unique rows. If you want to group the products together and show the correct quantity then you need to count the items.

   var report = printlist.GroupBy(x => x.ProductId)   //Group items by product id  
               .Select(group => new Vi_Sales_Detail () {          //For each group return back the product and the total # of items that match it  
                              ProductId = group.Key,   //The product that the group matches  
                              Quantity = group.Count()  //The # of items that are in group  
                           })  
               .ToList();   //Make a list out of it

Of course your Vi_Sales_Detail needs to have get/set properties that line up with the query I gave. Adjust accordingly.

djnilo dj 6 Reputation points

2022-12-16T19:13:46.31+00:00

Thank you very much for answering but I don't understand this Vi_Sales_Detail needs to have get/set properties that line up with the query I gave. Adjust accordingly.
Michael Taylor 60,161 Reputation points

2022-12-16T19:21:13.17+00:00
You didn't provide the definition of Vi_Sales_Detail. Since that is what your report variable is going to store, the Select method needs to return back an instance of that object. Since you want to capture the product ID and quantity in your report you need to ensure that you have properties in that type to back them. Something like this.

public class Vi_Sales_Detail { public int ProductId { get;set; } //Guessing on type here public int Quantity { get; set; } }

Previously you were using an anonymous type which won't work for you here.

djnilo dj 6

public partial class Vi_Sales_Detail  
     {  
         public int SaleID { get; set; }  
         public System.DateTime Date { get; set; }  
         public int IdDocumentType { get; set; }  
         public string Name { get; set; }  
         public int DocumentNum { get; set; }  
         public int CustomerID { get; set; }  
         public string CustomerName { get; set; }  
         public int PaymentFormID { get; set; }  
         public string PaymentFormName { get; set; }  
         public decimal VATPercent { get; set; }  
         public decimal SubTotal { get; set; }  
         public decimal Discount { get; set; }  
         public decimal VAT { get; set; }  
         public decimal Total { get; set; }  
         public int CommandId { get; set; }  
         public int State { get; set; }  
         public int detailId { get; set; }  
         public int ProductID { get; set; }  
         public string ProductName { get; set; }  
         public decimal Price { get; set; }  
         public decimal Quantity { get; set; }

Michael Taylor 60,161 Reputation points

2022-12-16T19:36:12.807+00:00
That should work. Just change ProductId to ProductID in the code I posted and the select statement should return the new object correctly. If you want additional data filled out in the object, such as product name or price, then you'll need to grab that as part of the select statement. Note that if you need access to the product data then you'll have to get it from one of the items in the list because you're grouping on the product Id (which doesn't have that data).

.Select(new Vi_Sales_Detail() { ..., ProductName = group.FirstOrDefault()?.ProductName, //Get the product's name });
djnilo dj 6 Reputation points

2022-12-16T20:31:50.563+00:00
reference error

var report = printList.GroupBy(x => x.ProductId) //Group items by product id
.Select(group => new Vi_Sales_Detail()
{
ProductId = group.Key, //The product that the group matches
Quantity = group.Count() //The # of items that are in group
})
.ToList(); //Make a list out of it

report = report;

djnilo dj 6

report = report;

             CreateTicket ticket = new CreateTicket();  
             ticket.TextoCentro("TICKET N° " + report[0].NumDocumento.ToString());  
             ticket.LeftText("");  
             ticket.TextoIzquierda("PHONE : " + phone);//added tigritos13-07-2022  
             ticket.LeftText("ADDRESS : " + address);  
             ticket.TextoIzquierda("TABLE : " + report[0].IdTable.ToString());  
             ticket.LinesEqual();  
             ticket.SaleHeader();  
             ticket.LinesEqual();  
             foreach (var item in report)  
             {  
                 ticket.AddItem(item.ProductName, Math.Round(item.Price, 0), item.Quantity, Math.Round(item.Price * item.Quantity, 0));  
             }  

             ticket.LinesEqual();  
             decimal subtotalCommand = 0;  
             foreach (var item in report)  
             {  

                 subtotalOrder = subtotalOrder + (item.Price * item.Quantity);  
             }  
             //Summary of the sale.  

             ticket.AddTotals(" SUBTOTAL......$", subtotalCommand);  
             ticket.AddTotals(" DISCOUNT.....$", report[0].Discount);  
             ticket.AddTotals(" TIP 10%...$", report[0].Tip10);

Michael Taylor 60,161 Reputation points

2022-12-16T21:23:44.853+00:00

You're going to have to debug this and tell us what the error is and where it is happening at. It could be anywhere in that query.Without any additional information printList could be null or you may have null objects inside it. In either case you need to handle that before the query. The focus of your question was on the query itself so that is where we focused.
djnilo dj 6 Reputation points

2022-12-17T04:06:13.227+00:00

report = printlist.GroupBy(x => x.ProductId) //Group items by product id
.Select(group => new Vi_Sales_Detail()
{
ProductId = group.Key, //The product that the group matches
Quantity = group.Count() //The # of items that are in group
})
.ToList(); //Make a list out of it

they do not enter these lines, the query bypasses, that is why the error
Michael Taylor 60,161 Reputation points

2022-12-19T15:04:54.3+00:00

Again, you're going to have to debug this. You asked for help with grouping in a LINQ query and now you're saying your code never even gets there. We have no context to help you with this. You posted this code in a method being called. If that method isn't being called then you need to step through your code to figure out why. That is what breakpoints are useful for.

If it is getting called then the grouping should be working correctly unless one of the objects is null. Stepping through your code would help identify that. If you're getting an error we need the error details.

Please clarify exactly what issue you're having, tell us the results of stepping through your code and if you're getting an error what the error message, type and callstack look like.

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linq query to display data

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