C# - LINQ - AggregateOperators

Example 1 - Count() (Unique)

int[] Array = { 2, 2, 3, 5, 5 }; 

int UniqueFactors = Array.Distinct().Count(); 

Console.WriteLine($"There are {UniqueFactors} unique factors."); 

//Output : There are 3 unique factors.

Example 2 - Count() (Conditional- Odd Number)

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

int oddNumbers = numbers.Count(n => n % 2 == 1);

Console.WriteLine("There are {0} odd numbers in the list.", oddNumbers);

//Output : There are 5 odd numbers in the list.

Example 3 - Count() (Count On Nested Collection Object )

List<Customer> customers = GetCustomerList();

var orderCounts = from c in customers

                  select (c.CustomerID, OrderCount: 

                                          c.Orders.Count()); 

                                            //Orders[]-Nested Collection

foreach (var customer in orderCounts)

{

    Console.WriteLine($"ID: {customer.CustomerID}, Count:    

                                          {customer.OrderCount}");

}

//Output

//ID: ALFKI, count: 6

//ID: ANATR, count: 4

//ID: ANTON, count: 7

//ID: AROUT, count: 13

//....

Example 4 - Count() (Grouped)

List<Product> products = GetProductList();

var categoryCounts = from p in products

                     group p by p.Category into g

                     select (Category: g.Key, ProductCount: g.Count());

                                       //-g.Key - Get the key of grouping

foreach (var c in categoryCounts)

{

     Console.WriteLine($"Category: {c.Category}: 

                         Product count: {c.ProductCount}");

}

//Output

//Category: Beverages: Product count: 12

//Category: Condiments: Product count: 12

//Category: Produce: Product count: 5

//Category: Meat / Poultry: Product count: 6

//Category: Seafood: Product count: 12

//Category: Dairy Products: Product count: 10

//Category: Confections: Product count: 13

//Category: Grains / Cereals: Product count: 7

Example 5 - SUM()

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

double numSum = numbers.Sum();

Console.WriteLine($"The sum of the numbers is {numSum}");

//The sum of the numbers is 45

Example 6 - SUM() (Projection)

string[] words = { "cherry", "apple", "blueberry" };

double totalChars = words.Sum(w => w.Length);

Console.WriteLine($"There are a total of {totalChars} characters in these words.");

//There are a total of 20 characters in these words.

Example 7 - SUM() (Grouped)

List<Product> products = GetProductList();

var categories = from p in products

                 group p by p.Category into g

                 select (Category: g.Key, TotalUnitsInStock:

                                   g.Sum(p => p.UnitsInStock));

foreach (var pair in categories)

{

    Console.WriteLine($"Category: {pair.Category},

                        Units in stock: {pair.TotalUnitsInStock}");

}

//Category: Beverages, Units in stock: 559

//Category: Condiments, Units in stock: 507

//Category: Produce, Units in stock: 100

//Category: Meat / Poultry, Units in stock: 165

//Category: Seafood, Units in stock: 701

//Category: Dairy Products, Units in stock: 393

//Category: Confections, Units in stock: 386

//Category: Grains / Cereals, Units in stock: 308

Example 8 - MIN()

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

int minNum = numbers.Min();

Console.WriteLine($"The minimum number is {minNum}");

//The minimum number is 0

Example 9 - MIN() (Projection)     

string[] words = { "cherry", "apple", "blueberry" };

int shortestWord = words.Min(w => w.Length);

Console.WriteLine($"The shortest word is {shortestWord} characters long.");

// The shortest word is 5 characters long.

Example 10 - MIN() (Grouped)     

List<Product> products = GetProductList();

var categories = from p in products

                 group p by p.Category into g

                 select (Category: g.Key,

                         CheapestPrice: g.Min(p => p.UnitPrice));

foreach (var c in categories)

{

    Console.WriteLine($"Category: {c.Category},

                       Lowest price: {c.CheapestPrice}");

}

//Output

//Category: Beverages, Lowest price: 4.5000

//Category: Condiments, Lowest price: 10.0000

//Category: Produce, Lowest price: 10.0000

//Category: Meat / Poultry, Lowest price: 7.4500

//Category: Seafood, Lowest price: 6.0000

//Category: Dairy Products, Lowest price: 2.5000

//Category: Confections, Lowest price: 9.2000

//Category: Grains / Cereals, Lowest price: 7.0000

Example 11 - MIN() (Grouped Each)     

List<Product> products = GetProductList();

var categories = from p in products

group p by p.Category into g

let minPrice = g.Min(p => p.UnitPrice)

select (Category: g.Key,

        CheapestProducts: g.Where(p => p.UnitPrice == minPrice));

foreach (var c in categories)

{

    Console.WriteLine($"Category: {c.Category}");

    foreach (var p in c.CheapestProducts)

    {

        Console.WriteLine($"\tProduct: {p}");

    }

}

//Output

//Category: Beverages

//Product: ProductID = 24 ProductName = Guaraná Fantástica Category = Beverages UnitPrice =$4.50 UnitsInStock = 20

//Category: Condiments

//Product: ProductID = 3 ProductName = Aniseed Syrup Category = Condiments UnitPrice =$10.00 UnitsInStock = 13

//Category: Produce

//Product: ProductID = 74 ProductName = Longlife Tofu Category = Produce UnitPrice =$10.00 UnitsInStock = 4

//Category: Meat / Poultry

//Product: ProductID = 54 ProductName = Tourtière Category = Meat / Poultry UnitPrice =$7.45 UnitsInStock = 21

//Category: Seafood

//Product: ProductID = 13 ProductName = Konbu Category = Seafood UnitPrice =$6.00 UnitsInStock = 24

//Category: Dairy Products

//Product: ProductID = 33 ProductName = Geitost Category = Dairy Products UnitPrice =$2.50 UnitsInStock = 112

//Category: Confections

//Product: ProductID = 19 ProductName = Teatime Chocolate Biscuits Category = Confections UnitPrice =$9.20 UnitsInStock = 25

//Category: Grains / Cereals

//Product: ProductID = 52 ProductName = Filo Mix Category = Grains / Cereals UnitPrice =$7.00 UnitsInStock = 38

Example 12 - MAX()

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

int maxNum = numbers.Max();

Console.WriteLine($"The maximum number is {maxNum}");

//The maximum number is 9

Example 13 - MAX() (Projection)

string[] words = { "cherry", "apple", "blueberry" };

int longestLength = words.Max(w => w.Length);

Console.WriteLine($"The longest word is {longestLength} characters long.");

//The longest word is 9 characters long.

Example 14 - MAX() (Grouped)

List<Product> products = GetProductList();

var categories = from p in products

                 group p by p.Category into g

                 select (Category: g.Key, MostExpensivePrice: g.Max(p => p.UnitPrice));

foreach (var c in categories)

{

       Console.WriteLine($"Category: {c.Category}

                          Most expensive product: {c.MostExpensivePrice}");

}

//Category: Beverages Most expensive product: 263.5000

//Category: Condiments Most expensive product: 43.9000

//Category: Produce Most expensive product: 53.0000

//Category: Meat / Poultry Most expensive product: 123.7900

//Category: Seafood Most expensive product: 62.5000

//Category: Dairy Products Most expensive product: 55.0000

//Category: Confections Most expensive product: 81.0000

//Category: Grains / Cereals Most expensive product: 38.0000

Example 15 - MAX() (Grouped Each)

List<Product> products = GetProductList();

var categories = from p in products

                 group p by p.Category into g

                 let maxPrice = g.Max(p => p.UnitPrice)

                 select (Category: g.Key,

                         MostExpensiveProducts: g.Where(p => p.UnitPrice == maxPrice));

foreach (var c in categories)

{

       Console.WriteLine($"Category: {c.Category}");

       foreach (var p in c.MostExpensiveProducts)

       {

              Console.WriteLine($"\t{p}");

       }

}

//Category: Beverages

//ProductID = 38 ProductName = Côte de Blaye Category = Beverages UnitPrice =$263.50 UnitsInStock = 17

//Category: Condiments

//ProductID = 63 ProductName = Vegie - spread Category = Condiments UnitPrice =$43.90 UnitsInStock = 24

//Category: Produce

//ProductID = 51 ProductName = Manjimup Dried Apples Category = Produce UnitPrice =$53.00 UnitsInStock = 20

//Category: Meat / Poultry

//ProductID = 29 ProductName = Thüringer Rostbratwurst Category = Meat / Poultry UnitPrice =$123.79 UnitsInStock = 0

//Category: Seafood

//ProductID = 18 ProductName = Carnarvon Tigers Category = Seafood UnitPrice =$62.50 UnitsInStock = 42

//Category: Dairy Products

//ProductID = 59 ProductName = Raclette Courdavault Category = Dairy Products UnitPrice =$55.00 UnitsInStock = 79

//Category: Confections

//ProductID = 20 ProductName = Sir Rodney's Marmalade Category=Confections UnitPrice=$81.00 UnitsInStock=40

//Category: Grains / Cereals

//ProductID = 56 ProductName = Gnocchi di nonna Alice Category = Grains / Cereals UnitPrice =$38.00 UnitsInStock = 21

Example 16 - AVERAGE()

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

double averageNum = numbers.Average();

Console.WriteLine($"The average number is {averageNum}.");

//The average number is 4.5.

Example 17 - AVERAGE() (Projection)

string[] words = { "cherry", "apple", "blueberry" };

double averageLength = words.Average(w => w.Length);

Console.WriteLine($"The average word length is {averageLength} characters.");

//The average word length is 6.66666666666667 characters.

Example 18 - AVERAGE()(Grouped)

List<Product> products = GetProductList();

var categories = from p in products

      group p by p.Category into g

      select (Category: g.Key,

              AveragePrice: g.Average(p => p.UnitPrice));

 foreach (var c in categories)

 {

     Console.WriteLine($"Category: {c.Category},

                         Average price: {c.AveragePrice}");

 }

 //Category: Beverages, Average price: 37.979166666666666666666666667

 //Category: Condiments, Average price: 23.0625

 //Category: Produce, Average price: 32.3700

 //Category: Meat / Poultry, Average price: 54.006666666666666666666666667

 //Category: Seafood, Average price: 20.6825

 //Category: Dairy Products, Average price: 28.7300

 //Category: Confections, Average price: 25.1600

 //Category: Grains / Cereals, Average price: 20.2500

Example 19 - Aggregate() (Grouped)

double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 };

double product = doubles.Aggregate((runningProduct, nextFactor) =>

                                                runningProduct * nextFactor);

Console.WriteLine($"Total product of all numbers: {product}");