<ExtensionAttribute> _
Public Shared Function OrderBy(Of TSource, TKey) ( _
    source As IEnumerable(Of TSource), _
    keySelector As Func(Of TSource, TKey) _
) As IOrderedEnumerable(Of TSource)

Dim source As IEnumerable(Of TSource)
Dim keySelector As Func(Of TSource, TKey)
Dim returnValue As IOrderedEnumerable(Of TSource)

returnValue = source.OrderBy(keySelector)

public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey>(
    this IEnumerable<TSource> source,
    Func<TSource, TKey> keySelector
)

[ExtensionAttribute]
public:
generic<typename TSource, typename TKey>
static IOrderedEnumerable<TSource>^ OrderBy(
    IEnumerable<TSource>^ source, 
    Func<TSource, TKey>^ keySelector
)

JScript does not support generic types or methods.

Usage Note

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.

To order a sequence by the values of the elements themselves, specify the identity function (x => x in Visual C# or Function(x) x in Visual Basic) for keySelector.

Two methods are defined to extend the type IOrderedEnumerable<(Of <(TElement>)>), which is the return type of this method. These two methods, namely ThenBy and ThenByDescending, enable you to specify additional sort criteria to sort a sequence. ThenBy and ThenByDescending also return an IOrderedEnumerable<(Of <(TElement>)>), which means any number of consecutive calls to ThenBy or ThenByDescending can be made.

Note:
Because IOrderedEnumerable<(Of <(TElement>)>) inherits from IEnumerable<(Of <(T>)>), you can call OrderBy or OrderByDescending on the results of a call to OrderBy, OrderByDescending, ThenBy or ThenByDescending. Doing this introduces a new primary ordering that ignores the previously established ordering.

This method compares keys by using the default comparer Default.

This method performs a stable sort; that is, if the keys of two elements are equal, the order of the elements is preserved. In contrast, an unstable sort does not preserve the order of elements that have the same key.

In query expression syntax, an orderby (Visual C#) or Order By (Visual Basic) clause translates to an invocation of OrderBy.

The following code example demonstrates how to use OrderBy<(Of <(TSource, TKey>)>)(IEnumerable<(Of <(TSource>)>), Func<(Of <(TSource, TKey>)>)) to sort the elements of a sequence.

Structure Pet
    Public Name As String
    Public Age As Integer
End Structure

Sub OrderByEx1()
    ' Create an array of Pet objects.
    Dim pets() As Pet = {New Pet With {.Name = "Barley", .Age = 8}, _
                         New Pet With {.Name = "Boots", .Age = 4}, _
                         New Pet With {.Name = "Whiskers", .Age = 1}}

    ' Order the Pet objects by their Age property.
    Dim query As IEnumerable(Of Pet) = _
        pets.OrderBy(Function(pet) pet.Age)

    Dim output As New System.Text.StringBuilder
    For Each pt As Pet In query
        output.AppendLine(pt.Name & " - " & pt.Age)
    Next

    ' Display the output.
    MsgBox(output.ToString())
End Sub

' This code produces the following output:
'
' Whiskers - 1
' Boots - 4
' Barley - 8

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void OrderByEx1()
{
    Pet[] pets = { new Pet { Name="Barley", Age=8 },
                   new Pet { Name="Boots", Age=4 },
                   new Pet { Name="Whiskers", Age=1 } };

    IEnumerable<Pet> query = pets.OrderBy(pet => pet.Age);

    foreach (Pet pet in query)
    {
        Console.WriteLine("{0} - {1}", pet.Name, pet.Age);
    }
}

/*
 This code produces the following output:

 Whiskers - 1
 Boots - 4
 Barley - 8
*/

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