Enumerable.Aggregate 方法

定義

多載

Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)

將累加函式套用到序列上。Applies an accumulator function over a sequence. 使用指定的值做為初始累加值,並使用指定的函式來選取結果值。The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.

Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>)

將累加函式套用到序列上。Applies an accumulator function over a sequence. 使用指定的初始值做為初始累加值。The specified seed value is used as the initial accumulator value.

Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>)

將累加函式套用到序列上。Applies an accumulator function over a sequence.

Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)

將累加函式套用到序列上。Applies an accumulator function over a sequence. 使用指定的值做為初始累加值,並使用指定的函式來選取結果值。The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.

public:
generic <typename TSource, typename TAccumulate, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static TResult Aggregate(System::Collections::Generic::IEnumerable<TSource> ^ source, TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> ^ func, Func<TAccumulate, TResult> ^ resultSelector);
public static TResult Aggregate<TSource,TAccumulate,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, TAccumulate seed, Func<TAccumulate,TSource,TAccumulate> func, Func<TAccumulate,TResult> resultSelector);
static member Aggregate : seq<'Source> * 'Accumulate * Func<'Accumulate, 'Source, 'Accumulate> * Func<'Accumulate, 'Result> -> 'Result
<Extension()>
Public Function Aggregate(Of TSource, TAccumulate, TResult) (source As IEnumerable(Of TSource), seed As TAccumulate, func As Func(Of TAccumulate, TSource, TAccumulate), resultSelector As Func(Of TAccumulate, TResult)) As TResult

類型參數

TSource

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

TAccumulate

累積值的類型。The type of the accumulator value.

TResult

結果值的類型。The type of the resulting value.

參數

source
IEnumerable<TSource>

所要彙總 (Aggregate) 的 IEnumerable<T>An IEnumerable<T> to aggregate over.

seed
TAccumulate

初始累積值。The initial accumulator value.

func
Func<TAccumulate,TSource,TAccumulate>

要在每個項目上叫用 (Invoke) 的累加函式。An accumulator function to be invoked on each element.

resultSelector
Func<TAccumulate,TResult>

用來將最終累加值轉換成結果值的函式。A function to transform the final accumulator value into the result value.

傳回

TResult

轉換後的最終累加值。The transformed final accumulator value.

例外狀況

sourcefuncresultSelectornullsource or func or resultSelector is null.

範例

下列程式碼範例示範如何使用 Aggregate 來套用累計函數和結果選取器。The following code example demonstrates how to use Aggregate to apply an accumulator function and a result selector.

string[] fruits = { "apple", "mango", "orange", "passionfruit", "grape" };

// Determine whether any string in the array is longer than "banana".
string longestName =
    fruits.Aggregate("banana",
                    (longest, next) =>
                        next.Length > longest.Length ? next : longest,
    // Return the final result as an upper case string.
                    fruit => fruit.ToUpper());

Console.WriteLine(
    "The fruit with the longest name is {0}.",
    longestName);

// This code produces the following output:
//
// The fruit with the longest name is PASSIONFRUIT.
Sub AggregateEx3()
    Dim fruits() As String =
    {"apple", "mango", "orange", "passionfruit", "grape"}

    ' Determine whether any string in the array is longer than "banana".
    Dim longestName As String =
    fruits.Aggregate("banana",
                     Function(ByVal longest, ByVal fruit) _
                         IIf(fruit.Length > longest.Length, fruit, longest),
                     Function(ByVal fruit) fruit.ToUpper())

    ' Display the output.
    MsgBox("The fruit with the longest name is " & longestName)
End Sub

' This code produces the following output:
'
' The fruit with the longest name is PASSIONFRUIT

備註

@No__t-0 方法可讓您輕鬆地對一連串的值執行計算。The Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>) method makes it simple to perform a calculation over a sequence of values. 這個方法的運作方式是針對 source 中的每個元素呼叫 func 一次。This method works by calling func one time for each element in source. 每次呼叫 func 時,Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>) 會同時傳遞序列中的元素和匯總值(做為 func 的第一個引數)。Each time func is called, Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>) passes both the element from the sequence and an aggregated value (as the first argument to func). @No__t-0 參數的值會用來做為初始匯總值。The value of the seed parameter is used as the initial aggregate value. @No__t-0 的結果會取代先前的匯總值。The result of func replaces the previous aggregated value. @No__t-0 的最終結果會傳遞給 resultSelector,以取得 Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>) 的最終結果。The final result of func is passed to resultSelector to obtain the final result of Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>).

為了簡化常見的匯總作業,標準查詢運算子也包括一般用途計數方法,Count 和四個數值匯總方法,亦即 MinMaxSumAverageTo simplify common aggregation operations, the standard query operators also include a general purpose count method, Count, and four numeric aggregation methods, namely Min, Max, Sum, and Average.

Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>)

將累加函式套用到序列上。Applies an accumulator function over a sequence. 使用指定的初始值做為初始累加值。The specified seed value is used as the initial accumulator value.

public:
generic <typename TSource, typename TAccumulate>
[System::Runtime::CompilerServices::Extension]
 static TAccumulate Aggregate(System::Collections::Generic::IEnumerable<TSource> ^ source, TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> ^ func);
public static TAccumulate Aggregate<TSource,TAccumulate> (this System.Collections.Generic.IEnumerable<TSource> source, TAccumulate seed, Func<TAccumulate,TSource,TAccumulate> func);
static member Aggregate : seq<'Source> * 'Accumulate * Func<'Accumulate, 'Source, 'Accumulate> -> 'Accumulate
<Extension()>
Public Function Aggregate(Of TSource, TAccumulate) (source As IEnumerable(Of TSource), seed As TAccumulate, func As Func(Of TAccumulate, TSource, TAccumulate)) As TAccumulate

類型參數

TSource

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

TAccumulate

累積值的類型。The type of the accumulator value.

參數

source
IEnumerable<TSource>

所要彙總 (Aggregate) 的 IEnumerable<T>An IEnumerable<T> to aggregate over.

seed
TAccumulate

初始累積值。The initial accumulator value.

func
Func<TAccumulate,TSource,TAccumulate>

要在每個項目上叫用 (Invoke) 的累加函式。An accumulator function to be invoked on each element.

傳回

TAccumulate

最終累積值。The final accumulator value.

例外狀況

sourcefuncnullsource or func is null.

範例

下列程式碼範例示範如何使用 Aggregate 來套用累計函數並使用初始值。The following code example demonstrates how to use Aggregate to apply an accumulator function and use a seed value.

int[] ints = { 4, 8, 8, 3, 9, 0, 7, 8, 2 };

// Count the even numbers in the array, using a seed value of 0.
int numEven = ints.Aggregate(0, (total, next) =>
                                    next % 2 == 0 ? total + 1 : total);

Console.WriteLine("The number of even integers is: {0}", numEven);

// This code produces the following output:
//
// The number of even integers is: 6
Sub AggregateEx2()
    ' Create an array of Integers.
    Dim ints() As Integer = {4, 8, 8, 3, 9, 0, 7, 8, 2}

    ' Count the even numbers in the array, using a seed value of 0.
    Dim numEven As Integer =
    ints.Aggregate(0,
                   Function(ByVal total, ByVal number) _
                       IIf(number Mod 2 = 0, total + 1, total))

    ' Display the output.
    MsgBox("The number of even integers is " & numEven)
End Sub

' This code produces the following output:
'
'The number of even integers is 6

備註

@No__t-0 方法可讓您輕鬆地對一連串的值執行計算。The Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>) method makes it simple to perform a calculation over a sequence of values. 這個方法的運作方式是針對 source 中的每個元素呼叫 func 一次。This method works by calling func one time for each element in source. 每次呼叫 func 時,Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>) 會同時傳遞序列中的元素和匯總值(做為 func 的第一個引數)。Each time func is called, Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>) passes both the element from the sequence and an aggregated value (as the first argument to func). @No__t-0 參數的值會用來做為初始匯總值。The value of the seed parameter is used as the initial aggregate value. @No__t-0 的結果會取代先前的匯總值。The result of func replaces the previous aggregated value. Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>) 會傳回 func 的最終結果。Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>) returns the final result of func.

為了簡化常見的匯總作業,標準查詢運算子也包括一般用途計數方法,Count 和四個數值匯總方法,亦即 MinMaxSumAverageTo simplify common aggregation operations, the standard query operators also include a general purpose count method, Count, and four numeric aggregation methods, namely Min, Max, Sum, and Average.

Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>)

將累加函式套用到序列上。Applies an accumulator function over a sequence.

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

類型參數

TSource

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

參數

source
IEnumerable<TSource>

所要彙總 (Aggregate) 的 IEnumerable<T>An IEnumerable<T> to aggregate over.

func
Func<TSource,TSource,TSource>

要在每個項目上叫用 (Invoke) 的累加函式。An accumulator function to be invoked on each element.

傳回

TSource

最終累積值。The final accumulator value.

例外狀況

sourcefuncnullsource or func is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Aggregate 來反轉字串中的單字順序。The following code example demonstrates how to reverse the order of words in a string by using Aggregate.

string sentence = "the quick brown fox jumps over the lazy dog";

// Split the string into individual words.
string[] words = sentence.Split(' ');

// Prepend each word to the beginning of the 
// new sentence to reverse the word order.
string reversed = words.Aggregate((workingSentence, next) =>
                                      next + " " + workingSentence);

Console.WriteLine(reversed);

// This code produces the following output:
//
// dog lazy the over jumps fox brown quick the
Sub AggregateEx1()
    Dim sentence As String =
    "the quick brown fox jumps over the lazy dog"
    ' Split the string into individual words.
    Dim words() As String = sentence.Split(" "c)
    ' Prepend each word to the beginning of the new sentence to reverse the word order.
    Dim reversed As String =
    words.Aggregate(Function(ByVal current, ByVal word) word & " " & current)

    ' Display the output.
    MsgBox(reversed)
End Sub

' This code produces the following output:
'
' dog lazy the over jumps fox brown quick the

備註

@No__t-0 方法可讓您輕鬆地對一連串的值執行計算。The Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>) method makes it simple to perform a calculation over a sequence of values. 這個方法的運作方式是針對 source 中的每個專案呼叫 func 一次,但第一個專案除外。This method works by calling func one time for each element in source except the first one. 每次呼叫 func 時,Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>) 會同時傳遞序列中的元素和匯總值(做為 func 的第一個引數)。Each time func is called, Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>) passes both the element from the sequence and an aggregated value (as the first argument to func). @No__t-0 的第一個元素會當做初始匯總值使用。The first element of source is used as the initial aggregate value. @No__t-0 的結果會取代先前的匯總值。The result of func replaces the previous aggregated value. Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>) 會傳回 func 的最終結果。Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>) returns the final result of func.

@No__t-0 方法的這個多載不適合所有案例,因為它會使用 source 的第一個元素做為初始匯總值。This overload of the Aggregate method isn't suitable for all cases because it uses the first element of source as the initial aggregate value. 如果傳回值只應包含符合特定條件之 source 的元素,您應該選擇另一個多載。You should choose another overload if the return value should include only the elements of source that meet a certain condition. 例如,如果您想要計算 source 中偶數的總和,則此多載不可靠。For example, this overload isn't reliable if you want to calculate the sum of the even numbers in source. 如果第一個專案是奇數,而不是偶數,則結果會是不正確的。The result will be incorrect if the first element is odd instead of even.

為了簡化常見的匯總作業,標準查詢運算子也包括一般用途計數方法,Count 和四個數值匯總方法,亦即 MinMaxSumAverageTo simplify common aggregation operations, the standard query operators also include a general purpose count method, Count, and four numeric aggregation methods, namely Min, Max, Sum, and Average.

適用於