1. 기본적인 LINQ 쿼리 문법

using System.Linq;

var numbers = new int[] { 1, 2, 3, 4, 5 };
var evenNumbers = from num in numbers
                  where num % 2 == 0
                  select num;

2. 메소드 체인을 사용한 LINQ

var oddNumbers = numbers.Where(num => num % 2 != 0).ToList();

3. 정렬 (Ordering)

var sortedNumbers = from num in numbers
                    orderby num descending
                    select num;

// 또는 메소드 체인을 사용하여
var sortedNumbersMethod = numbers.OrderByDescending(num => num).ToList();

4. 집계 함수 (Aggregation)

int sum = numbers.Sum();
int max = numbers.Max();
int min = numbers.Min();

5. 그룹화 (Grouping)

var groupedByParity = from num in numbers
                      group num by num % 2 into numGroup
                      select new { Parity = numGroup.Key, Numbers = numGroup };

// 또는 메소드 체인을 사용하여
var groupedByParityMethod = numbers.GroupBy(num => num % 2)
                                   .Select(g => new { Parity = g.Key, Numbers = g })
                                   .ToList();

6. 조인 (Join)

var products = new[] { new { Id = 1, Name = "Apple" }, new { Id = 2, Name = "Banana" } };
var orders = new[] { new { ProductId = 1, Quantity = 5 }, new { ProductId = 2, Quantity = 3 } };

var productOrders = from p in products
                    join o in orders on p.Id equals o.ProductId
                    select new { p.Name, o.Quantity };

7. 선택 (Projection)

var productNames = products.Select(p => p.Name).ToList();