Enumerable.AggregateEnumerable.AggregateEnumerable.AggregateEnumerable.Aggregate Method

重载

 Aggregate(IEnumerable, TAccumulate, Func, Func) Aggregate(IEnumerable, TAccumulate, Func, Func) Aggregate(IEnumerable, TAccumulate, Func, Func) Aggregate(IEnumerable, TAccumulate, Func, Func) 对序列应用累加器函数。Applies an accumulator function over a sequence. 将指定的种子值用作累加器的初始值，并使用指定的函数选择结果值。The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value. Aggregate(IEnumerable, TAccumulate, Func) Aggregate(IEnumerable, TAccumulate, Func) Aggregate(IEnumerable, TAccumulate, Func) Aggregate(IEnumerable, TAccumulate, Func) 对序列应用累加器函数。Applies an accumulator function over a sequence. 将指定的种子值用作累加器初始值。The specified seed value is used as the initial accumulator value. Aggregate(IEnumerable, Func) Aggregate(IEnumerable, Func) Aggregate(IEnumerable, Func) Aggregate(IEnumerable, Func) 对序列应用累加器函数。Applies an accumulator function over a sequence.

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

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

类型参数

TSource

source 的元素类型。The type of the elements of source.

TAccumulate

TResult

参数

source
IEnumerable<TSource>

seed
TAccumulate TAccumulate TAccumulate TAccumulate

func
Func<TAccumulate,TSource,TAccumulate>

resultSelector
Func<TAccumulate,TResult>

返回

TResult TResult TResult TResult

异常

sourcefuncresultSelectornullsource or func or resultSelector is null.

示例

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

注解

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. 此方法的工作方式func是对中source的每个元素调用一次。This method works by calling func one time for each element in source. 每次func调用时, Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)都会同时传递序列中的元素和聚合值 ( func作为的第一个参数)。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). seed参数的值用作初始聚合值。The value of the seed parameter is used as the initial aggregate value. 替换上一个func聚合值的结果。The result of func replaces the previous aggregated value. 的最终结果func传递到resultSelectorAggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)获取的最终结果。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>).

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

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

类型参数

TSource

source 的元素类型。The type of the elements of source.

TAccumulate

参数

source
IEnumerable<TSource>

seed
TAccumulate TAccumulate TAccumulate TAccumulate

func
Func<TAccumulate,TSource,TAccumulate>

返回

TAccumulate TAccumulate TAccumulate TAccumulate

异常

sourcefuncnullsource or func is null.

示例

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

注解

The Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>) method makes it simple to perform a calculation over a sequence of values. 此方法的工作方式func是对中source的每个元素调用一次。This method works by calling func one time for each element in source. 每次func调用时, Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>)都会同时传递序列中的元素和聚合值 ( func作为的第一个参数)。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). seed参数的值用作初始聚合值。The value of the seed parameter is used as the initial aggregate value. 替换上一个func聚合值的结果。The result of func replaces the previous aggregated value. Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>) returns the final result of func.

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

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

类型参数

TSource

source 的元素类型。The type of the elements of source.

参数

source
IEnumerable<TSource>

func
Func<TSource,TSource,TSource>

返回

TSource TSource TSource TSource

异常

sourcefuncnullsource or func is null.

source 中不包含任何元素。source contains no elements.

示例

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

注解

Aggregate方法的重载不适用于所有情况, 因为它使用的第一个source元素作为初始聚合值。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. 如果返回值仅应包含符合特定条件的元素source , 则应选择另一个重载。You should choose another overload if the return value should include only the elements of source that meet a certain condition. 例如, 如果要计算中source偶数的总和, 此重载并不可靠。For example, this overload isn't reliable if you want to calculate the sum of the even numbers in source. 如果第一个元素是奇数而不是偶数, 则结果将不正确。The result will be incorrect if the first element is odd instead of even.