Enumerable.OrderBy 方法

定義

依遞增順序排序序列中的項目。Sorts the elements of a sequence in ascending order.

多載

OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

依據索引鍵,按遞增順序排序序列中的項目。Sorts the elements of a sequence in ascending order according to a key.

OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)

使用指定的比較子,依遞增順序排序序列中的項目。Sorts the elements of a sequence in ascending order by using a specified comparer.

OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

依據索引鍵,按遞增順序排序序列中的項目。Sorts the elements of a sequence in ascending order according to a key.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IOrderedEnumerable<TSource> ^ OrderBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector);
public static System.Linq.IOrderedEnumerable<TSource> OrderBy<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector);
static member OrderBy : seq<'Source> * Func<'Source, 'Key> -> System.Linq.IOrderedEnumerable<'Source>
<Extension()>
Public Function OrderBy(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey)) As IOrderedEnumerable(Of TSource)

類型參數

TSource

source 項目的類型。The type of the elements of source.

TKey

keySelector 所傳回之索引鍵的型別。The type of the key returned by keySelector.

參數

source
IEnumerable<TSource>

要排序的值序列。A sequence of values to order.

keySelector
Func<TSource,TKey>

用來從項目擷取索引鍵的函式。A function to extract a key from an element.

傳回

依據索引鍵排序其項目的 IOrderedEnumerable<TElement>An IOrderedEnumerable<TElement> whose elements are sorted according to a key.

例外狀況

sourcekeySelectornullsource or keySelector is null.

範例

下列程式碼範例示範如何使用 OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) 來排序序列的元素。The following code example demonstrates how to use OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) to sort the elements of a sequence.

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
*/
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.
    Console.WriteLine(output.ToString())
End Sub

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

備註

這個方法是使用延後執行來執行。This method is implemented by using deferred execution. 立即傳回值是一個物件,它會儲存執行動作所需的所有資訊。The immediate return value is an object that stores all the information that is required to perform the action. 在列舉物件之前,不會執行此方法所代表的查詢,方法是直接呼叫其 GetEnumerator 方法,或是在 Visual Basic 中C#使用 Visual 或 For Each 中的 foreachThe 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.

若要依專案本身的值排序序列,請在 keySelector中指定識別函式(在C#視覺效果中為x => x,或在 Visual Basic 中為 Function(x) x)。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.

定義兩種方法來擴充類型 IOrderedEnumerable<TElement>,這是這個方法的傳回型別。Two methods are defined to extend the type IOrderedEnumerable<TElement>, which is the return type of this method. 這兩種方法(亦即 ThenByThenByDescending)可讓您指定其他排序準則來排序序列。These two methods, namely ThenBy and ThenByDescending, enable you to specify additional sort criteria to sort a sequence. ThenByThenByDescending 也會傳回 IOrderedEnumerable<TElement>,這表示可以對 ThenByThenByDescending 進行任意數目的連續呼叫。ThenBy and ThenByDescending also return an IOrderedEnumerable<TElement>, which means any number of consecutive calls to ThenBy or ThenByDescending can be made.

注意

因為 IOrderedEnumerable<TElement> 繼承自 IEnumerable<T>,所以您可以呼叫 OrderByOrderByDescendingThenByThenByDescending呼叫結果的 OrderByOrderByDescendingBecause IOrderedEnumerable<TElement> inherits from IEnumerable<T>, you can call OrderBy or OrderByDescending on the results of a call to OrderBy, OrderByDescending, ThenBy or ThenByDescending. 這麼做引進了新的主要順序,會忽略先前建立的順序。Doing this introduces a new primary ordering that ignores the previously established ordering.

這個方法會使用預設的比較子 Default來比較索引鍵。This method compares keys by using the default comparer Default.

這個方法會執行穩定的排序;也就是說,如果兩個元素的索引鍵相等,則會保留專案的順序。This method performs a stable sort; that is, if the keys of two elements are equal, the order of the elements is preserved. 相反地,不穩定的排序不會保留具有相同索引鍵的元素順序。In contrast, an unstable sort does not preserve the order of elements that have the same key.

在查詢運算式語法中,orderby (Visual C#)或 Order By (Visual Basic)子句會轉譯成 OrderBy的調用。In query expression syntax, an orderby (Visual C#) or Order By (Visual Basic) clause translates to an invocation of OrderBy.

另請參閱

OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)

使用指定的比較子,依遞增順序排序序列中的項目。Sorts the elements of a sequence in ascending order by using a specified comparer.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IOrderedEnumerable<TSource> ^ OrderBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, System::Collections::Generic::IComparer<TKey> ^ comparer);
public static System.Linq.IOrderedEnumerable<TSource> OrderBy<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, System.Collections.Generic.IComparer<TKey> comparer);
static member OrderBy : seq<'Source> * Func<'Source, 'Key> * System.Collections.Generic.IComparer<'Key> -> System.Linq.IOrderedEnumerable<'Source>
<Extension()>
Public Function OrderBy(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), comparer As IComparer(Of TKey)) As IOrderedEnumerable(Of TSource)

類型參數

TSource

source 項目的類型。The type of the elements of source.

TKey

keySelector 所傳回之索引鍵的型別。The type of the key returned by keySelector.

參數

source
IEnumerable<TSource>

要排序的值序列。A sequence of values to order.

keySelector
Func<TSource,TKey>

用來從項目擷取索引鍵的函式。A function to extract a key from an element.

comparer
IComparer<TKey>

用來比較金鑰的 IComparer<T>An IComparer<T> to compare keys.

傳回

依據索引鍵排序其項目的 IOrderedEnumerable<TElement>An IOrderedEnumerable<TElement> whose elements are sorted according to a key.

例外狀況

sourcekeySelectornullsource or keySelector is null.

備註

這個方法是使用延後執行來執行。This method is implemented by using deferred execution. 立即傳回值是一個物件,它會儲存執行動作所需的所有資訊。The immediate return value is an object that stores all the information that is required to perform the action. 在列舉物件之前,不會執行此方法所代表的查詢,方法是直接呼叫其 GetEnumerator 方法,或是在 Visual Basic 中C#使用 Visual 或 For Each 中的 foreachThe 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.

若要依專案本身的值排序序列,請在 keySelector中指定識別函式(在C#視覺效果中為x => x,或在 Visual Basic 中為 Function(x) x)。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.

定義兩種方法來擴充類型 IOrderedEnumerable<TElement>,這是這個方法的傳回型別。Two methods are defined to extend the type IOrderedEnumerable<TElement>, which is the return type of this method. 這兩種方法(亦即 ThenByThenByDescending)可讓您指定其他排序準則來排序序列。These two methods, namely ThenBy and ThenByDescending, enable you to specify additional sort criteria to sort a sequence. ThenByThenByDescending 也會傳回 IOrderedEnumerable<TElement>,這表示可以對 ThenByThenByDescending 進行任意數目的連續呼叫。ThenBy and ThenByDescending also return an IOrderedEnumerable<TElement>, which means any number of consecutive calls to ThenBy or ThenByDescending can be made.

注意

因為 IOrderedEnumerable<TElement> 繼承自 IEnumerable<T>,所以您可以呼叫 OrderByOrderByDescendingThenByThenByDescending呼叫結果的 OrderByOrderByDescendingBecause IOrderedEnumerable<TElement> inherits from IEnumerable<T>, you can call OrderBy or OrderByDescending on the results of a call to OrderBy, OrderByDescending, ThenBy or ThenByDescending. 這麼做引進了新的主要順序,會忽略先前建立的順序。Doing this introduces a new primary ordering that ignores the previously established ordering.

如果 null``comparer,則會使用預設的比較子 Default 來比較索引鍵。If comparer is null, the default comparer Default is used to compare keys.

這個方法會執行穩定的排序;也就是說,如果兩個元素的索引鍵相等,則會保留專案的順序。This method performs a stable sort; that is, if the keys of two elements are equal, the order of the elements is preserved. 相反地,不穩定的排序不會保留具有相同索引鍵的元素順序。In contrast, an unstable sort does not preserve the order of elements that have the same key.

另請參閱

適用於