Source:

Select.cs

Source:

Select.cs

Source:

Select.cs

Source:

Select.cs

public:generic <typename TSource, typename TResult>[System::Runtime::CompilerServices::Extension] static System::Collections::Generic::IEnumerable<TResult> ^ Select(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, int, TResult> ^ selector);

public static System.Collections.Generic.IEnumerable<TResult> Select<TSource,TResult>(this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,int,TResult> selector);

static member Select : seq<'Source> * Func<'Source, int, 'Result> -> seq<'Result>

<Extension()>Public Function Select(Of TSource, TResult) (source As IEnumerable(Of TSource), selector As Func(Of TSource, Integer, TResult)) As IEnumerable(Of TResult)

Type Parameters

Parameters

Returns

AnIEnumerable<T> whose elements are the result of invoking the transform function on each element ofsource.

Exceptions

Examples

The following code example demonstrates how to useSelect<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,TResult>) to project over a sequence of values and use the index of each element.

string[] fruits = { "apple", "banana", "mango", "orange",                      "passionfruit", "grape" };var query =    fruits.Select((fruit, index) =>                      new { index, str = fruit.Substring(0, index) });foreach (var obj in query){    Console.WriteLine("{0}", obj);}/* This code produces the following output: { index = 0, str =  } { index = 1, str = b } { index = 2, str = ma } { index = 3, str = ora } { index = 4, str = pass } { index = 5, str = grape }*/

' Create an array of strings.Dim fruits() As String ={"apple", "banana", "mango", "orange", "passionfruit", "grape"}' Project each item in the array to an anonymous type' that stores the item's index in the array and' a substring of each item whose length is equal' to the index position in the original array.Dim query =fruits.Select(Function(fruit, index) _                  New With {index, .Str = fruit.Substring(0, index)})Dim output As New System.Text.StringBuilderFor Each obj In query    output.AppendLine(obj.ToString())Next' Display the output.Console.WriteLine(output.ToString())' This code produces the following output:'' { index = 0, Str =  }' { index = 1, Str = b }' { index = 2, Str = ma }' { index = 3, Str = ora }' { index = 4, Str = pass }' { index = 5, Str = grape }

Remarks

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 itsGetEnumerator method directly or by usingforeach in C# orFor Each in Visual Basic.

The first argument toselector represents the element to process. The second argument toselector represents the zero-based index of that element in the source sequence. This can be useful if the elements are in a known order and you want to do something with an element at a particular index, for example. It can also be useful if you want to retrieve the index of one or more elements.

This projection method requires the transform function,selector, to produce one value for each value in the source sequence,source. Ifselector 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 theSelectMany method instead ofSelect. AlthoughSelectMany works similarly toSelect, it differs in that the transform function returns a collection that is then expanded bySelectMany before it is returned.

Source:

Select.cs

Source:

Select.cs

Source:

Select.cs

Source:

Select.cs

public:generic <typename TSource, typename TResult>[System::Runtime::CompilerServices::Extension] static System::Collections::Generic::IEnumerable<TResult> ^ Select(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TResult> ^ selector);

public static System.Collections.Generic.IEnumerable<TResult> Select<TSource,TResult>(this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TResult> selector);

static member Select : seq<'Source> * Func<'Source, 'Result> -> seq<'Result>

<Extension()>Public Function Select(Of TSource, TResult) (source As IEnumerable(Of TSource), selector As Func(Of TSource, TResult)) As IEnumerable(Of TResult)

Type Parameters

Parameters

Returns

AnIEnumerable<T> whose elements are the result of invoking the transform function on each element ofsource.

Exceptions

Examples

The following code example demonstrates how to useSelect<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*/

' Create a collection of sequential integers' from 1 to 10 and project their squares.Dim squares As IEnumerable(Of Integer) =Enumerable.Range(1, 10).Select(Function(x) x * x)Dim output As New System.Text.StringBuilderFor Each num As Integer In squares    output.AppendLine(num)Next' Display the output.Console.WriteLine(output.ToString())' This code produces the following output:'' 1' 4' 9' 16' 25' 36' 49' 64' 81' 100

Remarks

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 itsGetEnumerator method directly or by usingforeach in C# orFor Each in Visual Basic.

This projection method requires the transform function,selector, to produce one value for each value in the source sequence,source. Ifselector 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 theSelectMany method instead ofSelect. AlthoughSelectMany works similarly toSelect, it differs in that the transform function returns a collection that is then expanded bySelectMany before it is returned.

In query expression syntax, aselect (C#) orSelect (Visual Basic) clause translates to an invocation ofSelect.

See also

• select clause (C# Reference)
• Select Clause (Visual Basic)