101个Linq例子(40-60)

GroupBy - Simple 2

 public void Linq41()

    {

        string[] words = { "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" };

        var wordGroups =

            from w in words

            group w by w[] into g

            select new { FirstLetter = g.Key, Words = g };

        foreach (var g in wordGroups)

        {

            Console.WriteLine("Words that start with the letter '{0}':", g.FirstLetter);

            foreach (var w in g.Words)

            {

                Console.WriteLine(w);

            }

        }

    } 

Result

Words that start with the letter 'b':
blueberry
banana
Words that start with the letter 'c':
chimpanzee
cheese
Words that start with the letter 'a':
abacus
apple

GroupBy - Simple 3

 public void Linq42()

    {

        List<Product> products = GetProductList();

        var orderGroups =

            from p in products

            group p by p.Category into g

            select new { Category = g.Key, Products = g };

        ObjectDumper.Write(orderGroups, );

    } 

 Result

Category=Beverages Products=...
Products: ProductID=1 ProductName=Chai Category=Beverages UnitPrice=18.0000 UnitsInStock=39
Products: ProductID=2 ProductName=Chang Category=Beverages UnitPrice=19.0000 UnitsInStock=17
Products: ProductID=24 ProductName=Guaraná Fantástica Category=Beverages UnitPrice=4.5000 UnitsInStock=20
Products: ProductID=34 ProductName=Sasquatch Ale Category=Beverages UnitPrice=14.0000 UnitsInStock=111
Products: ProductID=35 ProductName=Steeleye Stout Category=Beverages UnitPrice=18.0000 UnitsInStock=20
Products: ProductID=38 ProductName=Côte de Blaye Category=Beverages UnitPrice=263.5000 UnitsInStock=17
Products: ProductID=39 ProductName=Chartreuse verte Category=Beverages UnitPrice=18.0000 UnitsInStock=69
Products: ProductID=43 ProductName=Ipoh Coffee Category=Beverages UnitPrice=46.0000 UnitsInStock=17
Products: ProductID=67 ProductName=Laughing Lumberjack Lager Category=Beverages UnitPrice=14.0000 UnitsInStock=52
Products: ProductID=70 ProductName=Outback Lager Category=Beverages UnitPrice=15.0000 UnitsInStock=15
Products: ProductID=75 ProductName=Rhönbräu Klosterbier Category=Beverages UnitPrice=7.7500 UnitsInStock=125
Products: ProductID=76 ProductName=Lakkalikööri Category=Beverages UnitPrice=18.0000 UnitsInStock=57
Category=Condiments Products=...
Products: ProductID=3 ProductName=Aniseed Syrup Category=Condiments UnitPrice=10.0000 UnitsInStock=13
Products: ProductID=4 ProductName=Chef Anton's Cajun Seasoning Category=Condiments UnitPrice=22.0000 UnitsInStock=53

GroupBy - Nested

   public void Linq43()

    {

        List<Customer> customers = GetCustomerList();

        var customerOrderGroups =

            from c in customers

            select

                new

                {

                    c.CompanyName,

                    YearGroups =

                        from o in c.Orders

                        group o by o.OrderDate.Year into yg

                        select

                            new

                            {

                                Year = yg.Key,

                                MonthGroups =

                                    from o in yg

                                    group o by o.OrderDate.Month into mg

                                    select new { Month = mg.Key, Orders = mg }

                            }

                };

        ObjectDumper.Write(customerOrderGroups, );

    }
 

Result

CompanyName=Alfreds Futterkiste YearGroups=...
YearGroups: Year=1997 MonthGroups=...
MonthGroups: Month=8 Orders=...
Orders: OrderID=10643 OrderDate=8/25/1997 Total=814.50
MonthGroups: Month=10 Orders=...
Orders: OrderID=10692 OrderDate=10/3/1997 Total=878.00
Orders: OrderID=10702 OrderDate=10/13/1997 Total=330.00
YearGroups: Year=1998 MonthGroups=...
MonthGroups: Month=1 Orders=...
Orders: OrderID=10835 OrderDate=1/15/1998 Total=845.80
MonthGroups: Month=3 Orders=...
Orders: OrderID=10952 OrderDate=3/16/1998 Total=471.20
MonthGroups: Month=4 Orders=...
Orders: OrderID=11011 OrderDate=4/9/1998 Total=933.50
CompanyName=Ana Trujillo Emparedados y helados YearGroups=...
YearGroups: Year=1996 MonthGroups=...
MonthGroups: Month=9 Orders=...
Orders: OrderID=10308 OrderDate=9/18/1996 Total=88.80
YearGroups: Year=1997 MonthGroups=...
MonthGroups: Month=8 Orders=...
Orders: OrderID=10625 OrderDate=8/8/1997 Total=479.75
MonthGroups: Month=11 Orders=...
Orders: OrderID=10759 OrderDate=11/28/1997 Total=320.00
YearGroups: Year=1998 MonthGroups=...
MonthGroups: Month=3 Orders=...

GroupBy - Comparer

 public void Linq44()

    {

        string[] anagrams = { "from   ", " salt", " earn ", "  last   ", " near ", " form  " };

        var orderGroups = anagrams.GroupBy(w => w.Trim(), new AnagramEqualityComparer());

        ObjectDumper.Write(orderGroups, );

    }

    public class AnagramEqualityComparer : IEqualityComparer<string>

    {

        public bool Equals(string x, string y)

        {

            return getCanonicalString(x) == getCanonicalString(y);

        }

        public int GetHashCode(string obj)

        {

            return getCanonicalString(obj).GetHashCode();

        }

        private string getCanonicalString(string word)

        {

            char[] wordChars = word.ToCharArray();

            Array.Sort<char>(wordChars);

            return new string(wordChars);

        }

    } 

Result

...
from 
form 
...
salt
last 
...
earn 
near

GroupBy - Comparer, Mapped

  public void Linq45()

    {

        string[] anagrams = { "from   ", " salt", " earn ", "  last   ", " near ", " form  " };

        var orderGroups = anagrams.GroupBy(

                    w => w.Trim(),

                    a => a.ToUpper(),

                    new AnagramEqualityComparer()

                    );

        ObjectDumper.Write(orderGroups, );

    }

    public class AnagramEqualityComparer : IEqualityComparer<string>

    {

        public bool Equals(string x, string y)

        {

            return getCanonicalString(x) == getCanonicalString(y);

        }

        public int GetHashCode(string obj)

        {

            return getCanonicalString(obj).GetHashCode();

        }

        private string getCanonicalString(string word)

        {

            char[] wordChars = word.ToCharArray();

            Array.Sort<char>(wordChars);

            return new string(wordChars);

        }

    } 

 Result

...
FROM 
FORM 
...
SALT
LAST 
...
EARN 
NEAR

Distinct - 1

public void Linq46()

{

    int[] factorsOf300 = { , , , ,  };

    var uniqueFactors = factorsOf300.Distinct();

    Console.WriteLine("Prime factors of 300:");

    foreach (var f in uniqueFactors)

    {

        Console.WriteLine(f);

    }

}

Result

Prime factors of 300:
2
3
5

Distinct - 2

public void Linq47()

{

    List<Product> products = GetProductList();

    var categoryNames = (

        from p in products

        select p.Category)

        .Distinct();

    Console.WriteLine("Category names:");

    foreach (var n in categoryNames)

    {

        Console.WriteLine(n);

    }

}

 Result

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

Union - 1

public void Linq48()

{

    int[] numbersA = { , , , , , ,  };

    int[] numbersB = { , , , ,  };

    var uniqueNumbers = numbersA.Union(numbersB);

    Console.WriteLine("Unique numbers from both arrays:");

    foreach (var n in uniqueNumbers)

    {

        Console.WriteLine(n);

    }

}

Result

Unique numbers from both arrays:
0
2
4
5
6
8
9
1
3
7

Union - 2

public void Linq49()

{

    List<Product> products = GetProductList();

    List<Customer> customers = GetCustomerList();

    var productFirstChars =

        from p in products

        select p.ProductName[];

    var customerFirstChars =

        from c in customers

        select c.CompanyName[];

    var uniqueFirstChars = productFirstChars.Union(customerFirstChars);

    Console.WriteLine("Unique first letters from Product names and Customer names:");

    foreach (var ch in uniqueFirstChars)

    {

        Console.WriteLine(ch);

    }

}

Result

Unique first letters from Product names and Customer names:
C
A
G
U
N
M
I
Q
K
T
P
S
R
B
J
Z
V
F
E
W
L
O
D
H

Intersect - 1

public void Linq50()

{

    int[] numbersA = { , , , , , ,  };

    int[] numbersB = { , , , ,  };

    var commonNumbers = numbersA.Intersect(numbersB);

    Console.WriteLine("Common numbers shared by both arrays:");

    foreach (var n in commonNumbers)

    {

        Console.WriteLine(n);

    }

}

 Result

Common numbers shared by both arrays:
5
8

Intersect - 2

public void Linq51()

{

    List<Product> products = GetProductList();

    List<Customer> customers = GetCustomerList();

    var productFirstChars =

        from p in products

        select p.ProductName[];

    var customerFirstChars =

        from c in customers

        select c.CompanyName[];

    var commonFirstChars = productFirstChars.Intersect(customerFirstChars);

    Console.WriteLine("Common first letters from Product names and Customer names:");

    foreach (var ch in commonFirstChars)

    {

        Console.WriteLine(ch);

    }

}

Result

Common first letters from Product names and Customer names:
C
A
G
N
M
I
Q
K
T
P
S
R
B
V
F
E
W
L
O

Except - 1

public void Linq52()

{

    int[] numbersA = { , , , , , ,  };

    int[] numbersB = { , , , ,  };

    IEnumerable<int> aOnlyNumbers = numbersA.Except(numbersB);

    Console.WriteLine("Numbers in first array but not second array:");

    foreach (var n in aOnlyNumbers)

    {

        Console.WriteLine(n);

    }

}

 Result

Numbers in first array but not second array:
0
2
4
6
9

Except - 2

public void Linq53()

{

    List<Product> products = GetProductList();

    List<Customer> customers = GetCustomerList();

    var productFirstChars =

        from p in products

        select p.ProductName[];

    var customerFirstChars =

        from c in customers

        select c.CompanyName[];

    var productOnlyFirstChars = productFirstChars.Except(customerFirstChars);

    Console.WriteLine("First letters from Product names, but not from Customer names:");

    foreach (var ch in productOnlyFirstChars)

    {

        Console.WriteLine(ch);

    }

}

Result

First letters from Product names, but not from Customer names:
U
J
Z

ToArray

public void Linq54()

{

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

    var sortedDoubles =

        from d in doubles

        orderby d descending

        select d;

    var doublesArray = sortedDoubles.ToArray();

    Console.WriteLine("Every other double from highest to lowest:");

    for (int d = ; d < doublesArray.Length; d += )

    {

        Console.WriteLine(doublesArray[d]);

    }

}

Result

Every other double from highest to lowest:
4.1
2.3
1.7

ToList

public void Linq55()

{

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

    var sortedWords =

        from w in words

        orderby w

        select w;

    var wordList = sortedWords.ToList();

    Console.WriteLine("The sorted word list:");

    foreach (var w in wordList)

    {

        Console.WriteLine(w);

    }

}

Result

The sorted word list:
apple
blueberry
cherry

ToDictionary

public void Linq56()

{

    var scoreRecords = new[] { new {Name = "Alice", Score = },

                                new {Name = "Bob"  , Score = },

                                new {Name = "Cathy", Score = }

                            };

    var scoreRecordsDict = scoreRecords.ToDictionary(sr => sr.Name);

    Console.WriteLine("Bob's score: {0}", scoreRecordsDict["Bob"]);

}

Result

Bob's score: { Name = Bob, Score = 40 }

OfType

public void Linq57()

{

    object[] numbers = { null, 1.0, "two", , "four", , "six", 7.0 };

    var doubles = numbers.OfType<double>();

    Console.WriteLine("Numbers stored as doubles:");

    foreach (var d in doubles)

    {

        Console.WriteLine(d);

    }

}

Result

Numbers stored as doubles:
1
7

First - Simple

public void Linq58()

{

    List<Product> products = GetProductList();

    Product product12 = (

        from p in products

        where p.ProductID ==

        select p)

        .First();

    ObjectDumper.Write(product12);

}

Result

ProductID=12 ProductName=Queso Manchego La Pastora Category=Dairy Products UnitPrice=38.0000 UnitsInStock=86

First - Condition

public void Linq59()

{

    string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    string startsWithO = strings.First(s => s[] == 'o');

    Console.WriteLine("A string starting with 'o': {0}", startsWithO);

}

Result

A string starting with 'o': one

FirstOrDefault - Simple

public void Linq61()

{

    int[] numbers = { };

    int firstNumOrDefault = numbers.FirstOrDefault();

    Console.WriteLine(firstNumOrDefault);

}

Result

0