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ParallelLoopState 類別

定義

讓平行迴圈的反覆項目與其他反覆項目互動。 Parallel 類別會在每個迴圈中提供這個類別的執行個體,您不能在自己的程式碼中建立執行個體。

public ref class ParallelLoopState
public class ParallelLoopState
type ParallelLoopState = class
Public Class ParallelLoopState
繼承
ParallelLoopState

範例

下列範例會平行執行迴圈最多 100 個反復專案。 每個反復專案都會暫停 1 到 1,000 毫秒的隨機間隔。 隨機產生的值會決定呼叫 方法的迴圈 Break 反覆運算。 如範例的輸出所示,在呼叫 Break 方法之後,索引大於 LowestBreakIteration 屬性值的反復專案。

using System;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
    public static void Main()
    {
        var rnd = new Random();
        int breakIndex = rnd.Next(1, 11);

        Console.WriteLine($"Will call Break at iteration {breakIndex}\n");

        var result = Parallel.For(1, 101, (i, state) => 
        {
            Console.WriteLine($"Beginning iteration {i}");
            int delay;
            lock (rnd)
                delay = rnd.Next(1, 1001);
            Thread.Sleep(delay);

            if (state.ShouldExitCurrentIteration)
            {
                if (state.LowestBreakIteration < i)
                    return;
            }

            if (i == breakIndex)
            {
                Console.WriteLine($"Break in iteration {i}");
                state.Break();
            }

            Console.WriteLine($"Completed iteration {i}");
        });

        if (result.LowestBreakIteration.HasValue)
            Console.WriteLine($"\nLowest Break Iteration: {result.LowestBreakIteration}");
        else
            Console.WriteLine($"\nNo lowest break iteration.");
    }
}
// The example displays output like the following:
//       Will call Break at iteration 8
//
//       Beginning iteration 1
//       Beginning iteration 13
//       Beginning iteration 97
//       Beginning iteration 25
//       Beginning iteration 49
//       Beginning iteration 37
//       Beginning iteration 85
//       Beginning iteration 73
//       Beginning iteration 61
//       Completed iteration 85
//       Beginning iteration 86
//       Completed iteration 61
//       Beginning iteration 62
//       Completed iteration 86
//       Beginning iteration 87
//       Completed iteration 37
//       Beginning iteration 38
//       Completed iteration 38
//       Beginning iteration 39
//       Completed iteration 25
//       Beginning iteration 26
//       Completed iteration 26
//       Beginning iteration 27
//       Completed iteration 73
//       Beginning iteration 74
//       Completed iteration 62
//       Beginning iteration 63
//       Completed iteration 39
//       Beginning iteration 40
//       Completed iteration 40
//       Beginning iteration 41
//       Completed iteration 13
//       Beginning iteration 14
//       Completed iteration 1
//       Beginning iteration 2
//       Completed iteration 97
//       Beginning iteration 98
//       Completed iteration 49
//       Beginning iteration 50
//       Completed iteration 87
//       Completed iteration 27
//       Beginning iteration 28
//       Completed iteration 50
//       Beginning iteration 51
//       Beginning iteration 88
//       Completed iteration 14
//       Beginning iteration 15
//       Completed iteration 15
//       Completed iteration 2
//       Beginning iteration 3
//       Beginning iteration 16
//       Completed iteration 63
//       Beginning iteration 64
//       Completed iteration 74
//       Beginning iteration 75
//       Completed iteration 41
//       Beginning iteration 42
//       Completed iteration 28
//       Beginning iteration 29
//       Completed iteration 29
//       Beginning iteration 30
//       Completed iteration 98
//       Beginning iteration 99
//       Completed iteration 64
//       Beginning iteration 65
//       Completed iteration 42
//       Beginning iteration 43
//       Completed iteration 88
//       Beginning iteration 89
//       Completed iteration 51
//       Beginning iteration 52
//       Completed iteration 16
//       Beginning iteration 17
//       Completed iteration 43
//       Beginning iteration 44
//       Completed iteration 44
//       Beginning iteration 45
//       Completed iteration 99
//       Beginning iteration 4
//       Completed iteration 3
//       Beginning iteration 8
//       Completed iteration 4
//       Beginning iteration 5
//       Completed iteration 52
//       Beginning iteration 53
//       Completed iteration 75
//       Beginning iteration 76
//       Completed iteration 76
//       Beginning iteration 77
//       Completed iteration 65
//       Beginning iteration 66
//       Completed iteration 5
//       Beginning iteration 6
//       Completed iteration 89
//       Beginning iteration 90
//       Completed iteration 30
//       Beginning iteration 31
//       Break in iteration 8
//       Completed iteration 8
//       Completed iteration 6
//       Beginning iteration 7
//       Completed iteration 7
//
//       Lowest Break Iteration: 8
Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      Dim breakIndex As Integer = rnd.Next(1, 11)
      Dim lowest As New Nullable(Of Long)()

      Console.WriteLine("Will call Break at iteration {0}", breakIndex)
      Console.WriteLine()

      Dim result = Parallel.For(1, 101, Sub(i, state)
                                            Console.WriteLine("Beginning iteration {0}", i)
                                            Dim delay As Integer
                                            Monitor.Enter(rnd)
                                               delay = rnd.Next(1, 1001)
                                            Monitor.Exit(rnd)
                                            Thread.Sleep(delay)

                                            If state.ShouldExitCurrentIteration Then
                                               If state.LowestBreakIteration < i Then
                                                  Return
                                               End If
                                            End If

                                            If i = breakIndex Then
                                               Console.WriteLine("Break in iteration {0}", i)
                                               state.Break()
                                               If state.LowestBreakIteration.HasValue Then
                                                  If lowest < state.LowestBreakIteration Then
                                                     lowest = state.LowestBreakIteration
                                                  Else
                                                     lowest = state.LowestBreakIteration
                                                  End If
                                               End If
                                            End If

                                            Console.WriteLine("Completed iteration {0}", i)
                                       End Sub )
         Console.WriteLine()
         If lowest.HasValue Then
            Console.WriteLine("Lowest Break Iteration: {0}", lowest)
         Else
            Console.WriteLine("No lowest break iteration.")
         End If
   End Sub
End Module
' The example displays output like the following:
'       Will call Break at iteration 8
'
'       Beginning iteration 1
'       Beginning iteration 13
'       Beginning iteration 97
'       Beginning iteration 25
'       Beginning iteration 49
'       Beginning iteration 37
'       Beginning iteration 85
'       Beginning iteration 73
'       Beginning iteration 61
'       Completed iteration 85
'       Beginning iteration 86
'       Completed iteration 61
'       Beginning iteration 62
'       Completed iteration 86
'       Beginning iteration 87
'       Completed iteration 37
'       Beginning iteration 38
'       Completed iteration 38
'       Beginning iteration 39
'       Completed iteration 25
'       Beginning iteration 26
'       Completed iteration 26
'       Beginning iteration 27
'       Completed iteration 73
'       Beginning iteration 74
'       Completed iteration 62
'       Beginning iteration 63
'       Completed iteration 39
'       Beginning iteration 40
'       Completed iteration 40
'       Beginning iteration 41
'       Completed iteration 13
'       Beginning iteration 14
'       Completed iteration 1
'       Beginning iteration 2
'       Completed iteration 97
'       Beginning iteration 98
'       Completed iteration 49
'       Beginning iteration 50
'       Completed iteration 87
'       Completed iteration 27
'       Beginning iteration 28
'       Completed iteration 50
'       Beginning iteration 51
'       Beginning iteration 88
'       Completed iteration 14
'       Beginning iteration 15
'       Completed iteration 15
'       Completed iteration 2
'       Beginning iteration 3
'       Beginning iteration 16
'       Completed iteration 63
'       Beginning iteration 64
'       Completed iteration 74
'       Beginning iteration 75
'       Completed iteration 41
'       Beginning iteration 42
'       Completed iteration 28
'       Beginning iteration 29
'       Completed iteration 29
'       Beginning iteration 30
'       Completed iteration 98
'       Beginning iteration 99
'       Completed iteration 64
'       Beginning iteration 65
'       Completed iteration 42
'       Beginning iteration 43
'       Completed iteration 88
'       Beginning iteration 89
'       Completed iteration 51
'       Beginning iteration 52
'       Completed iteration 16
'       Beginning iteration 17
'       Completed iteration 43
'       Beginning iteration 44
'       Completed iteration 44
'       Beginning iteration 45
'       Completed iteration 99
'       Beginning iteration 4
'       Completed iteration 3
'       Beginning iteration 8
'       Completed iteration 4
'       Beginning iteration 5
'       Completed iteration 52
'       Beginning iteration 53
'       Completed iteration 75
'       Beginning iteration 76
'       Completed iteration 76
'       Beginning iteration 77
'       Completed iteration 65
'       Beginning iteration 66
'       Completed iteration 5
'       Beginning iteration 6
'       Completed iteration 89
'       Beginning iteration 90
'       Completed iteration 30
'       Beginning iteration 31
'       Break in iteration 8
'       Completed iteration 8
'       Completed iteration 6
'       Beginning iteration 7
'       Completed iteration 7
'
'       Lowest Break Iteration: 8

因為呼叫 方法時 Break ,迴圈的反復專案仍可能會執行,所以每個反復專案都會呼叫 ShouldExitCurrentIteration 屬性,以檢查另一個反復專案是否呼叫 Break 方法。 如果屬性值為 true ,反覆運算會檢查 屬性的值 LowestBreakIteration ,如果大於目前反復專案的索引值,則會立即傳回 。

備註

請注意,您無法具現化這個類別的實例。 編譯器會自動產生為 或 Parallel.ForEach 方法呼叫 Parallel.For 中的引數。 這個範例將提供說明。

for在 C# ) 中建構 和 foreach (,以及 For Visual Basic 中的 (,) For Each 從最低索引到最高或從集合中第一個物件循序執行至最後一個物件。 相反地, Parallel.ForParallel.ForEach 方法不會。 因為迴圈的個別反復專案會以平行方式執行,所以可以依任何順序開始和結束。 類別 ParallelLoopState 可讓平行迴圈的個別反復專案彼此互動。 類別 ParallelLoopState 可讓您:

  • 結束目前的反復專案,並防止任何其他反復專案從 呼叫 Stop 方法開始。 這不會影響已經開始執行的反復專案。

  • 呼叫 方法,防止索引大於目前索引的任何反復專案執行 Break 。 這不會影響已經開始執行的反復專案。

  • 藉由擷取 屬性的值 IsExceptional ,判斷任何迴圈反覆運算中是否發生例外狀況。

  • 藉由擷取 屬性的值 IsStoppedStop 判斷迴圈的任何反復專案是否已呼叫 方法。 您可以使用這個屬性從呼叫 方法之前 Stop 啟動的迴圈反復專案傳回,但仍執行中。

  • 藉由擷取 屬性的值 ShouldExitCurrentIteration ,判斷迴圈的任何反復專案是否呼叫 BreakStop 方法,或已擲回例外狀況。

  • 從長時間執行的反復專案結束,其索引大於呼叫 Break 的反復專案索引,方法是擷取 屬性的值 LowestBreakIteration

屬性

IsExceptional

取得迴圈中是否有任何反覆項目已擲回該反覆項目未處理的例外狀況。

IsStopped

取得迴圈中是否有任何反覆項目已呼叫 Stop() 方法。

LowestBreakIteration

取得迴圈中呼叫 Break() 的最低反覆項目。

ShouldExitCurrentIteration

取得是否應該根據迴圈中目前這個或其他反覆項目的要求,來結束目前這個反覆項目。

方法

Break()

傳達 Parallel 迴圈應該在過了目前的反覆項目之後,依系統的方便盡早停止執行反覆項目。

Equals(Object)

判斷指定的物件是否等於目前的物件。

(繼承來源 Object)
GetHashCode()

做為預設雜湊函式。

(繼承來源 Object)
GetType()

取得目前執行個體的 Type

(繼承來源 Object)
MemberwiseClone()

建立目前 Object 的淺層複製。

(繼承來源 Object)
Stop()

傳達 Parallel 迴圈應該依系統的方便盡早停止執行。

ToString()

傳回代表目前物件的字串。

(繼承來源 Object)

適用於

執行緒安全性

ParallelLoopState實例只用于提供實例的迴圈主體內。 在相關聯的迴圈結束時,使用提供的 ParallelLoopState 實例並不安全,也無法安全地將它交給其他執行緒,並讓這些執行緒隨時存取它。 系統會將不同的 ParallelLoopState 實例提供給迴圈中涉及的每個執行緒。

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