Enumerable.Aggregate 方法

來源:

Aggregate.cs

來源:

Aggregate.cs

來源:

Aggregate.cs

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

參數

傳回

轉換後的最終累加值。

例外狀況

範例

下列程式代碼範例示範如何使用 來套用 Aggregate 累積函數和結果選取器。

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.
    Console.WriteLine($"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

方法 Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>) 可讓您輕鬆地對值序列執行計算。 此方法的運作方式是針對 中的每個source項目呼叫func一次。 每次呼叫時，Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)都會func將序列中的 項目和匯總值傳遞 (做為第一個自變數來 func) 。 參數的值 seed 會當做初始匯總值使用。 的結果 func 會取代先前的匯總值。 的最終結果 func 會傳遞至 resultSelector ，以取得的最終結果 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含一般用途的計數方法、 Count和四個數值匯總方法，也就是 Min、 MaxSum和 Average。

來源:

Aggregate.cs

來源:

Aggregate.cs

來源:

Aggregate.cs

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

參數

傳回

最終累積值。

例外狀況

範例

下列程式代碼範例示範如何使用 來套用 Aggregate 累積函數，並使用種子值。

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.
    Console.WriteLine($"The number of even integers is {numEven}")
End Sub

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

備註

方法 Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>) 可讓您輕鬆地對值序列執行計算。 此方法的運作方式是針對 中的每個source項目呼叫func一次。 每次呼叫時，Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>)都會func將序列中的 項目和匯總值傳遞 (做為第一個自變數來 func) 。 參數的值 seed 會當做初始匯總值使用。 的結果 func 會取代先前的匯總值。 Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>) 傳回的最終結果 func。

為了簡化常見的匯總作業，標準查詢運算子也包含一般用途的計數方法、 Count和四個數值匯總方法，也就是 Min、 MaxSum和 Average。

來源:

Aggregate.cs

來源:

Aggregate.cs

來源:

Aggregate.cs

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

參數

傳回

最終累積值。

例外狀況

範例

下列程式代碼範例示範如何使用 來反轉字串 Aggregate中的單字順序。

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.
    Console.WriteLine(reversed)
End Sub

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

備註

方法 Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>) 可讓您輕鬆地對值序列執行計算。 此方法的運作方式是針對中每個元素呼叫 func 一次，但第一個元素 source 除外。 每次呼叫時，Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>)都會func將序列中的 項目和匯總值傳遞 (做為第一個自變數來 func) 。 的第一個元素 source 會當做初始匯總值使用。 的結果 func 會取代先前的匯總值。 Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>) 傳回的最終結果 func。

此方法的 Aggregate 這個多載不適用於所有情況，因為它使用 的第一個專案 source 做為初始匯總值。 如果傳回值只包含符合特定條件的 source 元素，您應該選擇另一個多載。 例如，如果您想要計算 中 source偶數的總和，這個多載並不可靠。 如果第一個專案是奇數，而不是偶數，則結果會不正確。

為了簡化常見的匯總作業，標準查詢運算子也包含一般用途的計數方法、 Count和四個數值匯總方法，也就是 Min、 MaxSum和 Average。