Projection Operations in LINQ
Projection is an operation in which an object is transformed into an altogether new form with only specific properties.
Operator | Description | C# Query Expression Syntax | VB Query Expression Syntax |
---|---|---|---|
Select | The operator projects values on basis of a transform function | select | Select |
SelectMany | The operator project the sequences of values which are based on a transform function as well as flattens them into a single sequence | Use multiple from clauses | Use multiple From clauses |
Example of Select - Query Expression
C#
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Operators { class Program { static void Main(string[] args) { List<string> words = new List<string>() { "an", "apple", "a", "day" }; var query = from word in words select word.Substring(0, 1); foreach (string s in query) Console.WriteLine(s); Console.ReadLine(); } } }
VB
Module Module1 Sub Main() Dim words = New List(Of String) From {"an", "apple", "a", "day"} Dim query = From word In words Select word.Substring(0, 1); Dim sb As New System.Text.StringBuilder() For Each letter As String In query sb.AppendLine(letter) Console.WriteLine(letter) Next Console.ReadLine() End Sub End Module
When the above code in C# or VB is compiled and executed, it produces the following result −
a a a d
Example of SelectMany - Query Expression
C#
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Operators { class Program { static void Main(string[] args) { List<string> phrases = new List<string>() { "an apple a day", "the quick brown fox" }; var query = from phrase in phrases from word in phrase.Split(' ') select word; foreach (string s in query) Console.WriteLine(s); Console.ReadLine(); } } }
VB
Module Module1 Sub Main() Dim phrases = New List(Of String) From {"an apple a day", "the quick brown fox"} Dim query = From phrase In phrases From word In phrase.Split(" "c) Select word; Dim sb As New System.Text.StringBuilder() For Each str As String In query sb.AppendLine(str) Console.WriteLine(str) Next Console.ReadLine() End Sub End Module
When the above code in C# or VB is compiled and executed, it produces the following result −
an apple a day the quick brown fox
linq_query_operators.htm
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