C#
Summary - LINQ methods
Combine Any, Sum, Distinct and Take to write a sales report.
Summary - LINQ methods
In this group you learned extra LINQ methods: Any/All condition checks, Count/Sum/Average/Min/Max aggregates, Distinct/Contains set ops, Take/Skip slicing, ToDictionary/ToList conversion.
In the final lesson you will write a sales report: check with Any whether there is at least one big sale, sum amounts with Sum, dedupe customers with Distinct, and show the top three sales with Take.
Exercise Write a sales report
In the sales list: (1) check with Any whether there is at least one sale over 1000 and print the result; (2) print the total of all amounts with Sum; (3) sort with OrderByDescending and print the top two amounts with Take(2) in a foreach loop.
Show example solution
Console.WriteLine(sales.Any(s => s.Amount > 1000)); Console.WriteLine(sales.Sum(s => s.Amount)); foreach (var s in sales.OrderByDescending(s => s.Amount).Take(2)) Console.WriteLine(s.Amount);
Example solution:
using System;
using System.Collections.Generic;
using System.Linq;
class Sale
{
public int Amount { get; set; }
}
class Program
{
static void Main()
{
var sales = new List<Sale>
{
new Sale { Amount = 500 },
new Sale { Amount = 1500 },
new Sale { Amount = 800 },
new Sale { Amount = 2000 }
};
Console.WriteLine(sales.Any(s => s.Amount > 1000));
Console.WriteLine(sales.Sum(s => s.Amount));
foreach (var s in sales.OrderByDescending(s => s.Amount).Take(2))
{
Console.WriteLine(s.Amount);
}
}
}
Exercise Find distinct amounts
Take the amounts from the sales list with Select, deduplicate with Distinct and print each in a foreach loop.
Show example solution
Build sales.Select(s => s.Amount).Distinct(), loop with foreach, print with Console.WriteLine(a).
Example solution:
using System;
using System.Collections.Generic;
using System.Linq;
class Sale
{
public int Amount { get; set; }
}
class Program
{
static void Main()
{
var sales = new List<Sale>
{
new Sale { Amount = 500 },
new Sale { Amount = 500 },
new Sale { Amount = 800 },
new Sale { Amount = 800 }
};
foreach (var a in sales.Select(s => s.Amount).Distinct())
{
Console.WriteLine(a);
}
}
}
Test yourself
-
Which method gives the total?
- Average()
- Sum()
- Distinct()
- Take(n)
Show answer
Distinct() — Correct. Sum() gives the total of a numeric collection.
-
Match each method to its purpose
- Any
- At least one
- Sum
- Total
- Distinct
- Deduplicate
- Take
- First n elements
Next lesson: File.ReadAllText
