C#•2w ago

Linq+File

Can you give me some tips ? I only created seed file info writer to create and fill file with data (Step 1 and 2) Let's make two txt.file 1) Customers.txt 2) Orders.txt Customers table 3: CustomerID, CustomerName 1|Lasha 2|Beka 3|Dimitri Orders table : OrderID, Date, Product, Price, CustomerID 1|20201212|Coca-cola|3.0|1 2|20201111|Pepsi|3.0/2 3|20200909|Staropramen|4.0/2 4|20201212|Argo|2.0|3 There must be at least 5 users and at least 20 orders. (Fill in the details as you wish) We need to extract the following type of report: 1. The number of orders for each customer. For example: CustomerID - 1, Order Count-2 The total price of each customer's orders. For example: CustomerID - 1, SumAmount -2 10.5 3. Minimum order price for each customer. For example: CustomerID - 1, MinAmount-0.6 4. Only customers who have more than one order. CustomerID-1, Order Count-2 5. Only customers whose average order is greater than 10. CustomerID-1, AvgAmount-12.5 Best solution is with Aggregate functions in Ling, as well as Having clauses in Ling. Classic Foreach should only be used when printing.

8 Replies

この世界には人の運命をつかさどる何らかの超越的な「律」OP•2w ago

i can't understand one thing i need to take data from file like this ?

        var data2 = File.ReadAllLines(path);

        var data2 = File.ReadAllLines(path);

Pobiega•2w ago

That seems reasonable, yes. The way LINQ works is that it works on sequences, and if you use that method your files are read into string arrays, aka a sequence of strings

この世界には人の運命をつかさどる何らかの超越的な「律」OP•2w ago

var customers = data.Select(line => line.Split('|')).Select(m => new Customer{
            CustomerId = int.Parse([0]),
            CustomerName = m[1]
        });

var customers = data.Select(line => line.Split('|')).Select(m => new Customer{
            CustomerId = int.Parse([0]),
            CustomerName = m[1]
        });

i'll make the same for orders and then join them by ID and after i'll make main task yes it's ugly code , but i'm not using AI and struggling by myself (i've some knowledge , but s*ck at basics ...)

Pobiega•2w ago

No thats fine not ugly at all, pretty standard for "linq golf" 🙂 you missed an m on the int.Parse btw 😛

Angius•2w ago

Though, if you want to make LINQ pretty, newlines are your friend You usually see

var foo = bar
    .Where(x => ...)
    .Select(x => ...)
    .OrderBy(x => ...)
    .GroupBy(x => ...)
    .FirstOrDefault(x => ...);

var foo = bar
    .Where(x => ...)
    .Select(x => ...)
    .OrderBy(x => ...)
    .GroupBy(x => ...)
    .FirstOrDefault(x => ...);

rather than

var foo = bar.Where(x => ...).Select(x => ...).OrderBy(x => ...).GroupBy(x => ...).FirstOrDefault(x => ...);

var foo = bar.Where(x => ...).Select(x => ...).OrderBy(x => ...).GroupBy(x => ...).FirstOrDefault(x => ...);

この世界には人の運命をつかさどる何らかの超越的な「律」OP•2w ago

The number of orders for each customer. For example: CustomerID - 1, Order Count-2 For this i wanted to group orders by customer ids and then count for each customer , but since using foreach is forbidden i'm confused

Pobiega•2w ago

wdym? you dont need to group and even if you did, you wouldnt need a foreach

この世界には人の運命をつかさどる何らかの超越的な「律」OP•2w ago

       var orderCount = orders.GroupBy(o => o.CustomerId).Select(g=> new
       {
           CustomerId = g.Key,
           OrderCount = g.Count()
       }).ToList();
       foreach (var order in orderCount)
       {
           Console.WriteLine($"Customer ID {order.CustomerId} Order Count {order.OrderCount}");
       }

       var orderCount = orders.GroupBy(o => o.CustomerId).Select(g=> new
       {
           CustomerId = g.Key,
           OrderCount = g.Count()
       }).ToList();
       foreach (var order in orderCount)
       {
           Console.WriteLine($"Customer ID {order.CustomerId} Order Count {order.OrderCount}");
       }

yeah you are right i was bit confused cuz couldnot get grouped values from IEnumerable<Grouping>

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