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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