Information
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

Enumerable.Select<TSource, TResult> Method (IEnumerable<TSource>, Func<TSource, TResult>)

Projects each element of a sequence into a new form.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)

public static IEnumerable<TResult> Select<TSource, TResult>(
	this IEnumerable<TSource> source,
	Func<TSource, TResult> selector
)

Type Parameters

TSource

The type of the elements of source.

TResult

The type of the value returned by selector.

Parameters

source
Type: System.Collections.Generic.IEnumerable<TSource>

A sequence of values to invoke a transform function on.

selector
Type: System.Func<TSource, TResult>

A transform function to apply to each element.

Return Value

Type: System.Collections.Generic.IEnumerable<TResult>
An IEnumerable<T> whose elements are the result of invoking the transform function on each element of source.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

ExceptionCondition
ArgumentNullException

source or selector is null.

This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

This projection method requires the transform function, selector, to produce one value for each value in the source sequence, source. If selector returns a value that is itself a collection, it is up to the consumer to traverse the subsequences manually. In such a situation, it might be better for your query to return a single coalesced sequence of values. To achieve this, use the SelectMany method instead of Select. Although SelectMany works similarly to Select, it differs in that the transform function returns a collection that is then expanded by SelectMany before it is returned.

In query expression syntax, a select (Visual C#) or Select (Visual Basic) clause translates to an invocation of Select.

The following code example demonstrates how to use Select<TSource, TResult>(IEnumerable<TSource>, Func<TSource, TResult>) to project over a sequence of values.

IEnumerable<int> squares =
    Enumerable.Range(1, 10).Select(x => x * x);

foreach (int num in squares)
{
    Console.WriteLine(num);
}
/*
 This code produces the following output:

 1
 4
 9
 16
 25
 36
 49
 64
 81
 100
*/

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5

.NET Compact Framework

Supported in: 3.5

XNA Framework

Supported in: 3.0

Community Additions

Show:
© 2014 Microsoft