LINQ生成操作

新序列的值是由生成運算符創建的。

操作

描述

C#查詢表達式語法

VB查詢表達式語法

默認空

當應用於一個空的序列，產生一個序列內的默認元素

不適用

不適用

空

返回值是空序列，是最簡單的代操作符

不適用

不適用

範圍

產生具有整數或數字序列的集合

不適用

不適用

重複

生成包含特定長度的重複值的序列

不適用

不適用

DefaultIfEmpty例子 - Enumerable.DefaultIfEmpty.Method

C#

using System; using System.Collections.Generic; using System.Linq; namespace Operators { class DefaultEmpty { static void Main(string[] args) { Pet barley = new Pet() { Name = "Barley", Age = 4 }; Pet boots = new Pet() { Name = "Boots", Age = 1 }; Pet whiskers = new Pet() { Name = "Whiskers", Age = 6 }; Pet bluemoon = new Pet() { Name = "Blue Moon", Age = 9 }; Pet daisy = new Pet() { Name = "Daisy", Age = 3 }; List<Pet> pets = new List<Pet>() { barley, boots, whiskers, bluemoon, daisy }; foreach (var e in pets.DefaultIfEmpty()) { Console.WriteLine("Name = {0} ", e.Name); } Console.WriteLine("\nPress any key to continue."); Console.ReadKey(); } class Pet { public string Name { get; set; } public int Age { get; set; } } } }

VB

Module Module1 Sub Main() Dim barley As New Pet With {.Name = "Barley", .Age = 4} Dim boots As New Pet With {.Name = "Boots", .Age = 1} Dim whiskers As New Pet With {.Name = "Whiskers", .Age = 6} Dim bluemoon As New Pet With {.Name = "Blue Moon", .Age = 9} Dim daisy As New Pet With {.Name = "Daisy", .Age = 3} Dim pets As New System.Collections.Generic.List(Of Pet)(New Pet() {barley, boots, whiskers, bluemoon, daisy}) For Each e In pets.DefaultIfEmpty() Console.WriteLine("Name = {0}", e.Name) Next Console.WriteLine(vbLf & "Press any key to continue.") Console.ReadKey() End Sub Class Pet Public Property Name As String Public Property Age As Integer End Class End Module

當C＃或VB的上述代碼被編譯和執行時，它產生了以下結果：

Name = Barley
Name = Boots
Name = Whiskers
Name = Blue Moon
Name = Daisy

Press any key to contiue.

Range例子- Enumerable.Range方法

C#

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Operators { class Program { static void Main(string[] args) { // Generate a sequence of integers from 1 to 5 // and then select their squares. IEnumerable squares = Enumerable.Range(1, 5).Select(x => x * x); foreach (int num in squares) { Console.WriteLine(num); } Console.ReadLine(); } } }

VB

Module Module1 Sub Main() Dim squares As IEnumerable(Of Integer) = _ Enumerable.Range(1, 5).Select(Function(x) x * x) Dim output As New System.Text.StringBuilder For Each num As Integer In squares
output.AppendLine(num) Console.WriteLine(num) Next Console.ReadLine() End Sub End Module

當C＃或VB的上述代碼被編譯和執行時，它產生了以下結果：

1
4
9
16
25

Repeat例子- Enumerable.Repeat(TResult)方法

C#

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Operators { class Program { static void Main(string[] args) { IEnumerable strings = Enumerable.Repeat("I like programming.", 3); foreach (String str in strings) { Console.WriteLine(str); } Console.ReadLine(); } } }

VB

Module Module1 Sub Main() Dim sentences As IEnumerable(Of String) = _ Enumerable.Repeat("I like programming.", 3) Dim output As New System.Text.StringBuilder For Each sentence As String In sentences
output.AppendLine(sentence) Console.WriteLine(sentence) Next Console.ReadLine() End Sub End Module

當C＃或VB的上述代碼被編譯和執行時，它產生了以下結果：

I like programming.
I like programming.
I like programming.