LINQ - Aggregate Operators

Introduction

This sample shows different uses of Aggregate Operators:

• Count - Simple
• Count - Conditional
• Count - Nested
• Count - Grouped
• Sum - Simple
• Sum - Projection
• Sum - Grouped
• Min - Simple
• Min - Projection
• Min - Grouped
• Min - Elements
• Max - Simple
• Max - Projection
• Max - Grouped
• Max - Elements
• Average - Simple
• Average - Projection
• Average - Grouped
• Aggregate - Simple
• Aggregate - Seed

Description

Count - Simple  

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This sample uses Count to get the number of unique factors of 300.

C#

public void Linq73()
{
    int[] factorsOf300 = { 2, 2, 3, 5, 5 };
 
    int uniqueFactors = factorsOf300.Distinct().Count();
 
    Console.WriteLine("There are {0} unique factors of 300.", uniqueFactors);
}

 Result

There are 3 unique factors of 300.

Count - Conditional

This sample uses Count to get the number of odd ints in the array.

C#

public void Linq74()
{
    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);
}

Result

There are 5 odd numbers in the list.

Count - Nested

This sample uses Count to return a list of customers and how many orders each has.

C#

public void Linq76()
{
    List<Customer> customers = GetCustomerList();
 
    var orderCounts =
        from c in customers
        select new { c.CustomerID, OrderCount = c.Orders.Count() };
 
    ObjectDumper.Write(orderCounts);
}

Result

CustomerID=ALFKI CustomerID=ANATR CustomerID=ANTON CustomerID=AROUT CustomerID=BERGS CustomerID=BLAUS CustomerID=BLONP CustomerID=BOLID CustomerID=BONAP CustomerID=BOTTM CustomerID=BSBEV CustomerID=CACTU CustomerID=CENTC CustomerID=CHOPS CustomerID=COMMI CustomerID=CONSH CustomerID=DRACD CustomerID=DUMON CustomerID=EASTC CustomerID=ERNSH CustomerID=FAMIA CustomerID=FISSA CustomerID=FOLIG CustomerID=FOLKO CustomerID=FRANK CustomerID=FRANR CustomerID=FRANS CustomerID=FURIB CustomerID=GALED CustomerID=GODOS CustomerID=GOURL CustomerID=GREAL CustomerID=GROSR CustomerID=HANAR CustomerID=HILAA CustomerID=HUNGC CustomerID=HUNGO CustomerID=ISLAT CustomerID=KOENE CustomerID=LACOR CustomerID=LAMAI CustomerID=LAUGB CustomerID=LAZYK CustomerID=LEHMS CustomerID=LETSS CustomerID=LILAS CustomerID=LINOD CustomerID=LONEP CustomerID=MAGAA CustomerID=MAISD CustomerID=MEREP CustomerID=MORGK CustomerID=NORTS CustomerID=OCEAN CustomerID=OLDWO CustomerID=OTTIK CustomerID=PARIS CustomerID=PERIC CustomerID=PICCO CustomerID=PRINI CustomerID=QUEDE CustomerID=QUEEN CustomerID=QUICK CustomerID=RANCH CustomerID=RATTC CustomerID=REGGC CustomerID=RICAR CustomerID=RICSU CustomerID=ROMEY CustomerID=SANTG CustomerID=SAVEA CustomerID=SEVES CustomerID=SIMOB CustomerID=SPECD CustomerID=SPLIR CustomerID=SUPRD CustomerID=THEBI CustomerID=THECR CustomerID=TOMSP CustomerID=TORTU CustomerID=TRADH CustomerID=TRAIH CustomerID=VAFFE CustomerID=VICTE CustomerID=VINET CustomerID=WANDK CustomerID=WARTH CustomerID=WELLI CustomerID=WHITC CustomerID=WILMK CustomerID=WOLZA

OrderCount=6 OrderCount=4 OrderCount=7 OrderCount=13 OrderCount=18 OrderCount=7 OrderCount=11 OrderCount=3 OrderCount=17 OrderCount=14 OrderCount=10 OrderCount=6 OrderCount=1 OrderCount=8 OrderCount=5 OrderCount=3 OrderCount=6 OrderCount=4 OrderCount=8 OrderCount=30 OrderCount=7 OrderCount=0 OrderCount=5 OrderCount=19 OrderCount=15 OrderCount=3 OrderCount=6 OrderCount=8 OrderCount=5 OrderCount=10 OrderCount=9 OrderCount=11 OrderCount=2 OrderCount=14 OrderCount=18 OrderCount=5 OrderCount=19 OrderCount=10 OrderCount=14 OrderCount=4 OrderCount=14 OrderCount=3 OrderCount=2 OrderCount=15 OrderCount=4 OrderCount=14 OrderCount=12 OrderCount=8 OrderCount=10 OrderCount=7 OrderCount=13 OrderCount=5 OrderCount=3 OrderCount=5 OrderCount=10 OrderCount=9 OrderCount=0 OrderCount=6 OrderCount=10 OrderCount=6 OrderCount=9 OrderCount=13 OrderCount=28 OrderCount=5 OrderCount=18 OrderCount=12 OrderCount=11 OrderCount=10 OrderCount=5 OrderCount=6 OrderCount=31 OrderCount=9 OrderCount=7 OrderCount=4 OrderCount=9 OrderCount=12 OrderCount=4 OrderCount=3 OrderCount=5 OrderCount=10 OrderCount=7 OrderCount=3 OrderCount=11 OrderCount=10 OrderCount=4 OrderCount=10 OrderCount=15 OrderCount=9 OrderCount=14 OrderCount=8 OrderCount=7

Count - Grouped

This sample uses Count to return a list of categories and how many products each has.

C#

public void Linq77()
{
    List<Product> products = GetProductList();
 
    var categoryCounts =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, ProductCount = g.Count() };
 
    ObjectDumper.Write(categoryCounts
}

Result

Category=Beverages Category=Condiments Category=Produce Category=Meat/Poultry Category=Seafood Category=Dairy Products Category=Confections Category=Grains/Cereals

ProductCount=12 ProductCount=12 ProductCount=5 ProductCount=6 ProductCount=12 ProductCount=10 ProductCount=13 ProductCount=7

Sum - Simple

This sample uses Sum to get the total of the numbers in an array.

C#

public void Linq78()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
 
    double numSum = numbers.Sum();
 
    Console.WriteLine("The sum of the numbers is {0}.", numSum);
}

 Result

The sum of the numbers is 45.

Sum - Projection

This sample uses Sum to get the total number of characters of all words in the array.

C#

public void Linq79()
{
    string[] words = { "cherry", "apple", "blueberry" };
 
    double totalChars = words.Sum(w => w.Length);
 
    Console.WriteLine("There are a total of {0} characters in these words.", totalChars);
}

Result

There are a total of 20 characters in these words.

Sum - Grouped

This sample uses Sum to get the total units in stock for each product category.

C#

public void Linq80()
{
    List<Product> products = GetProductList();
 
    var categories =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, TotalUnitsInStock = g.Sum(p => p.UnitsInStock) };
 
    ObjectDumper.Write(categories);
}

Result

Category=Beverages Category=Condiments Category=Produce Category=Meat/Poultry Category=Seafood Category=Dairy Products Category=Confections Category=Grains/Cereals

TotalUnitsInStock=559 TotalUnitsInStock=507 TotalUnitsInStock=100 TotalUnitsInStock=165 TotalUnitsInStock=701 TotalUnitsInStock=393 TotalUnitsInStock=386 TotalUnitsInStock=308

Min - Simple

This sample uses Min to get the lowest number in an array.

C#

public void Linq81()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
 
    int minNum = numbers.Min();
 
    Console.WriteLine("The minimum number is {0}.", minNum);
}

Result

The minimum number is 0.

Min - Projection

This sample uses Min to get the length of the shortest word in an array.

C#

public void Linq82()
{
    string[] words = { "cherry", "apple", "blueberry" };
 
    int shortestWord = words.Min(w => w.Length);
 
    Console.WriteLine("The shortest word is {0} characters long.", shortestWord);
}

Result

The shortest word is 5 characters long.

Min - Grouped

This sample uses Min to get the cheapest price among each category's products.

C#

public void Linq83()
{
    List<Product> products = GetProductList();
 
    var categories =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, CheapestPrice = g.Min(p => p.UnitPrice) };
 
    ObjectDumper.Write(categories);
}

Result

Category=Beverages Category=Condiments Category=Produce Category=Meat/Poultry Category=Seafood Category=Dairy Products Category=Confections Category=Grains/Cereals

CheapestPrice=4.5000 CheapestPrice=10.0000 CheapestPrice=10.0000 CheapestPrice=7.4500 CheapestPrice=6.0000 CheapestPrice=2.5000 CheapestPrice=9.2000 CheapestPrice=7.0000

Min - Elements

This sample uses Min to get the products with the cheapest price in each category.

C#

public void Linq84()
{
    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 new { Category = g.Key, CheapestProducts = g.Where(p => p.UnitPrice == minPrice) };
 
    ObjectDumper.Write(categories, 1);
}

Result

Category=Beverages      CheapestProducts=...
  CheapestProducts: ProductID=24  ProductName=Guaraná Fantástica  Category=Beverages      UnitPrice=4.5000        UnitsInStock=20
Category=Condiments    CheapestProducts=...
  CheapestProducts: ProductID=3  ProductName=Aniseed Syrup      Category=Condiments    UnitPrice=10.0000      UnitsInStock=13
Category=Produce        CheapestProducts=...
  CheapestProducts: ProductID=74  ProductName=Longlife Tofu      Category=Produce        UnitPrice=10.0000      UnitsInStock=4
Category=Meat/Poultry  CheapestProducts=...
  CheapestProducts: ProductID=54  ProductName=Tourtière  Category=Meat/Poultry  UnitPrice=7.4500        UnitsInStock=21
Category=Seafood        CheapestProducts=...
  CheapestProducts: ProductID=13  ProductName=Konbu      Category=Seafood        UnitPrice=6.0000        UnitsInStock=24
Category=Dairy Products        CheapestProducts=...
  CheapestProducts: ProductID=33  ProductName=Geitost    Category=Dairy Products        UnitPrice=2.5000        UnitsInStock=112
Category=Confections    CheapestProducts=...
  CheapestProducts: ProductID=19  ProductName=Teatime Chocolate Biscuits  Category=Confections    UnitPrice=9.2000        UnitsInStock=25
Category=Grains/Cereals        CheapestProducts=...
  CheapestProducts: ProductID=52  ProductName=Filo Mix    Category=Grains/Cereals        UnitPrice=7.0000        UnitsInStock=38

Max - Simple

This sample uses Max to get the highest number in an array.

C#

public void Linq85()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
 
    int maxNum = numbers.Max();
 
    Console.WriteLine("The maximum number is {0}.", maxNum);
}

Result

The maximum number is 9.

Max - Projection

This sample uses Max to get the length of the longest word in an array.

C#

public void Linq86()
{
    string[] words = { "cherry", "apple", "blueberry" };
 
    int longestLength = words.Max(w => w.Length);
 
    Console.WriteLine("The longest word is {0} characters long.", longestLength);
}

Result

The longest word is 9 characters long.

Max - Grouped

This sample uses Max to get the most expensive price among each category's products.

C#

public void Linq87()
{
    List<Product> products = GetProductList();
 
    var categories =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, MostExpensivePrice = g.Max(p => p.UnitPrice) };
 
    ObjectDumper.Write(categories);
}

Result

Category=Beverages Category=Condiments Category=Produce Category=Meat/Poultry Category=Seafood Category=Dairy Products Category=Confections Category=Grains/Cereals

MostExpensivePrice=263.5000 MostExpensivePrice=43.9000 MostExpensivePrice=53.0000 MostExpensivePrice=123.7900 MostExpensivePrice=62.5000 MostExpensivePrice=55.0000 MostExpensivePrice=81.0000 MostExpensivePrice=38.0000

Max - Elements

This sample uses Max to get the products with the most expensive price in each category.

C#

public void Linq88()
{
    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 new { Category = g.Key, MostExpensiveProducts = g.Where(p => p.UnitPrice == maxPrice) };
 
    ObjectDumper.Write(categories, 1);
}

Result

Category=Beverages      MostExpensiveProducts=...
  MostExpensiveProducts: ProductID=38    ProductName=Côte de Blaye      Category=Beverages      UnitPrice=263.5000      UnitsInStock=17
Category=Condiments    MostExpensiveProducts=...
  MostExpensiveProducts: ProductID=63    ProductName=Vegie-spread        Category=Condiments    UnitPrice=43.9000      UnitsInStock=24
Category=Produce        MostExpensiveProducts=...
  MostExpensiveProducts: ProductID=51    ProductName=Manjimup Dried Apples      Category=Produce        UnitPrice=53.0000      UnitsInStock=20
Category=Meat/Poultry  MostExpensiveProducts=...
  MostExpensiveProducts: ProductID=29    ProductName=Thüringer Rostbratwurst    Category=Meat/Poultry  UnitPrice=123.7900      UnitsInStock=0
Category=Seafood        MostExpensiveProducts=...
  MostExpensiveProducts: ProductID=18    ProductName=Carnarvon Tigers    Category=Seafood        UnitPrice=62.5000      UnitsInStock=42
Category=Dairy Products        MostExpensiveProducts=...
  MostExpensiveProducts: ProductID=59    ProductName=Raclette Courdavault        Category=Dairy Products        UnitPrice=55.0000      UnitsInStock=79
Category=Confections    MostExpensiveProducts=...
  MostExpensiveProducts: ProductID=20    ProductName=Sir Rodney's Marmalade      Category=Confections    UnitPrice=81.0000      UnitsInStock=40
Category=Grains/Cereals        MostExpensiveProducts=...
  MostExpensiveProducts: ProductID=56    ProductName=Gnocchi di nonna Alice      Category=Grains/Cereals        UnitPrice=38.0000      UnitsInStock=21

Average - Simple

This sample uses Average to get the average of all numbers in an array.

C#

public void Linq89()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
 
    double averageNum = numbers.Average();
 
    Console.WriteLine("The average number is {0}.", averageNum);
}

Result

The average number is 4.5.

Average - Projection

This sample uses Average to get the average length of the words in the array.

C#

public void Linq90()
{
    string[] words = { "cherry", "apple", "blueberry" };
 
    double averageLength = words.Average(w => w.Length);
 
    Console.WriteLine("The average word length is {0} characters.", averageLength);
}

Result

The average word length is 6.66666666666667 characters.

Average - Grouped

This sample uses Average to get the average price of each category's products.

C#

public void Linq91()
{
    List<Product> products = GetProductList();
 
    var categories =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, AveragePrice = g.Average(p => p.UnitPrice) };
 
    ObjectDumper.Write(categories);
}

Result

Category=Beverages Category=Condiments Category=Produce Category=Meat/Poultry Category=Seafood Category=Dairy Products Category=Confections Category=Grains/Cereals

AveragePrice=37.979166666666666666666666667 AveragePrice=23.0625 AveragePrice=32.3700 AveragePrice=54.006666666666666666666666667 AveragePrice=20.6825 AveragePrice=28.7300 AveragePrice=25.1600 AveragePrice=20.2500

Aggregate - Simple

This sample uses Aggregate to create a running product on the array that calculates the total product of all elements.

C#

public void Linq92()
{
    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: {0}", product);
}

Result

Total product of all numbers: 88.33081

Aggregate - Seed

This sample uses Aggregate to create a running account balance that subtracts each withdrawal from the initial balance of 100, as long as the balance never drops below 0.

C#

public void Linq93()
{
    double startBalance = 100.0;
 
    int[] attemptedWithdrawals = { 20, 10, 40, 50, 10, 70, 30 };
 
    double endBalance =
        attemptedWithdrawals.Aggregate(startBalance,
            (balance, nextWithdrawal) =>
                ((nextWithdrawal <= balance) ? (balance - nextWithdrawal) : balance));
 
    Console.WriteLine("Ending balance: {0}", endBalance);
}

Result

Ending balance: 20