Monitor.TryEnter 方法

定义

命名空间:
System.Threading
程序集:
mscorlib.dll, System.Threading.dll
程序集:
netstandard.dll, System.Threading.dll
程序集:
System.Threading.dll
程序集:
mscorlib.dll
程序集:
netstandard.dll

尝试获取指定对象的排他锁。

重载

名称 说明
TryEnter(Object, TimeSpan, Boolean)

尝试在指定时间内获取指定对象的排他锁，并原子地设置一个值，该值指示是否已获取锁。
TryEnter(Object, Int32, Boolean)

尝试在指定毫秒内获取指定对象的排他锁，并原子地设置一个值，该值指示是否已获取锁。
TryEnter(Object, TimeSpan)

尝试在指定时间内获取指定对象的排他锁。
TryEnter(Object, Boolean)

尝试获取指定对象的排他锁，并原子地设置一个值，该值指示是否已获取锁。
TryEnter(Object)

尝试获取指定对象的排他锁。
TryEnter(Object, Int32)

尝试获取指定对象上的排他锁的指定毫秒数。

TryEnter(Object, TimeSpan, Boolean)

Source:
Monitor.cs
Source:
Monitor.cs
Source:
Monitor.cs
Source:
Monitor.cs
Source:
Monitor.cs

尝试在指定时间内获取指定对象的排他锁，并原子地设置一个值，该值指示是否已获取锁。

public:
 static void TryEnter(System::Object ^ obj, TimeSpan timeout, bool % lockTaken);
public static void TryEnter(object obj, TimeSpan timeout, ref bool lockTaken);
static member TryEnter : obj * TimeSpan * bool -> unit
Public Shared Sub TryEnter (obj As Object, timeout As TimeSpan, ByRef lockTaken As Boolean)

参数

obj
Object

要在其上获取锁的对象。

timeout
TimeSpan

等待锁的时间量。 -1 毫秒的值指定无限等待。

lockTaken
Boolean

尝试获取锁的结果，由引用传递。 输入必须是 false。 输出是 true 如果获取锁，则输出为 ;否则，输出为 false。 即使尝试获取锁期间发生异常，也会设置输出。

例外

ArgumentException

要输入 lockTaken 的为 true.

ArgumentNullException

参数 obj 为 null.

ArgumentOutOfRangeException

以毫秒为单位的值 timeout 为负值，且不等于 Infinite （-1 毫秒），或大于 Int32.MaxValue。

注解

如果参数的值 timeout 转换为毫秒等于 -1，则此方法等效 Enter(Object)于 。 如果值为 timeout 0，则此方法等效于 TryEnter(Object)。

如果未因为引发异常而锁定，则为 lockTaken 参数指定的变量在 false 此方法结束后。 这允许程序在所有情况下确定是否有必要释放锁。

Note

用于 Monitor 锁定对象（即引用类型），而不是值类型。 有关详细信息，请参阅 Monitor 类主题。

若要确保线程未进入关键节，应仅在关键节的值 lockTaken 为时检查并执行关键节中的代码的值 true。 以下代码片段显示了用于调用此方法的模式。 请注意，应在块中finally调用Exit，以确保调用线程在发生异常时释放关键节上的锁。

var lockObj = new Object();
var timeout = TimeSpan.FromMilliseconds(500);
bool lockTaken = false;

try {
   Monitor.TryEnter(lockObj, timeout, ref lockTaken);
   if (lockTaken) {
      // The critical section.
   }
   else {
      // The lock was not acquired.
   }
}
finally {
   // Ensure that the lock is released.
   if (lockTaken) {
      Monitor.Exit(lockObj);
   }
}

Dim lockObj As New Object()
Dim timeout = TimeSpan.FromMilliseconds(500)
Dim lockTaken As Boolean = False

Try
   Monitor.TryEnter(lockObj, timeout, lockTaken)
   If lockTaken Then
      ' The critical section.
   Else
      ' The lock was not acquired.
   End If
Finally
   ' Ensure that the lock is released.
   If lockTaken Then Monitor.Exit(lockObj)
End Try

另请参阅

适用于

TryEnter(Object, Int32, Boolean)

Source:
Monitor.CoreCLR.cs
Source:
Monitor.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs

尝试在指定毫秒内获取指定对象的排他锁，并原子地设置一个值，该值指示是否已获取锁。

public:
 static void TryEnter(System::Object ^ obj, int millisecondsTimeout, bool % lockTaken);
public static void TryEnter(object obj, int millisecondsTimeout, ref bool lockTaken);
static member TryEnter : obj * int * bool -> unit
Public Shared Sub TryEnter (obj As Object, millisecondsTimeout As Integer, ByRef lockTaken As Boolean)

参数

obj
Object

要在其上获取锁的对象。

millisecondsTimeout
Int32

等待锁的毫秒数。

lockTaken
Boolean

尝试获取锁的结果，由引用传递。 输入必须是 false。 输出是 true 如果获取锁，则输出为 ;否则，输出为 false。 即使尝试获取锁期间发生异常，也会设置输出。

例外

ArgumentException

要输入 lockTaken 的为 true.

ArgumentNullException

参数 obj 为 null.

ArgumentOutOfRangeException

millisecondsTimeout 为负数，且不等于 Infinite。

示例

以下代码显示了使用 TryEnter(Object, Boolean) 方法重载的基本模式。 此重载始终设置传递给 ref 参数 （ByRef in Visual Basic） lockTaken 的变量的值，即使该方法引发异常，变量的值也是测试锁是否必须释放的可靠方法。

bool acquiredLock = false;

try
{
    Monitor.TryEnter(lockObject, 500, ref acquiredLock);
    if (acquiredLock)
    {

        // Code that accesses resources that are protected by the lock.
    }
    else
    {
    
        // Code to deal with the fact that the lock was not acquired.
    }
}
finally
{
    if (acquiredLock)
    {
        Monitor.Exit(lockObject);
    }
}

Dim acquiredLock As Boolean = False

Try
    Monitor.TryEnter(lockObject, 500, acquiredLock)
    If acquiredLock Then

        ' Code that accesses resources that are protected by the lock.

    Else

        ' Code to deal with the fact that the lock was not acquired.

    End If
Finally
    If acquiredLock Then
        Monitor.Exit(lockObject)
    End If
End Try

注解

millisecondsTimeout如果参数相等Infinite，则此方法等效Enter(Object)于 。 如果 millisecondsTimeout 等于 0，则此方法等效于 TryEnter(Object)。

如果未因为引发异常而锁定，则为 lockTaken 参数指定的变量在 false 此方法结束后。 这允许程序在所有情况下确定是否有必要释放锁。

Note

用于 Monitor 锁定对象（即引用类型），而不是值类型。 有关详细信息，请参阅 Monitor 类主题。

若要确保线程未进入关键节，应仅在关键节的值 lockTaken 为时检查并执行关键节中的代码的值 true。 以下代码片段显示了用于调用此方法的模式。 请注意，应在块中finally调用Exit，以确保调用线程在发生异常时释放关键节上的锁。

var lockObj = new Object();
int timeout = 500;
bool lockTaken = false;

try {
   Monitor.TryEnter(lockObj, timeout, ref lockTaken);
   if (lockTaken) {
      // The critical section.
   }
   else {
      // The lock was not acquired.
   }
}
finally {
   // Ensure that the lock is released.
   if (lockTaken) {
      Monitor.Exit(lockObj);
   }   
}

Dim lockObj As New Object()
Dim timeout As Integer = 500
Dim lockTaken As Boolean = False

Try
   Monitor.TryEnter(lockObj, timeout, lockTaken)
   If lockTaken Then
      ' The critical section.
   Else
      ' The lock was not acquired.
   End If
Finally
   ' Ensure that the lock is released.
   If lockTaken Then Monitor.Exit(lockObj)
End Try

适用于

TryEnter(Object, TimeSpan)

Source:
Monitor.cs
Source:
Monitor.cs
Source:
Monitor.cs
Source:
Monitor.cs
Source:
Monitor.cs

尝试在指定时间内获取指定对象的排他锁。

public:
 static bool TryEnter(System::Object ^ obj, TimeSpan timeout);
public static bool TryEnter(object obj, TimeSpan timeout);
static member TryEnter : obj * TimeSpan -> bool
Public Shared Function TryEnter (obj As Object, timeout As TimeSpan) As Boolean

参数

obj
Object

要在其上获取锁的对象。

timeout
TimeSpan

一个 TimeSpan 表示等待锁的时间量。 -1 毫秒的值指定无限等待。

返回

Boolean

true 如果当前线程获取锁，则为否则，为 false.

例外

ArgumentNullException

参数 obj 为 null.

ArgumentOutOfRangeException

以毫秒为单位的值 timeout 为负值，且不等于 Infinite （-1 毫秒），或大于 Int32.MaxValue。

注解

如果参数的值 timeout 转换为毫秒等于 -1，则此方法等效 Enter于 。 如果值为 timeout 0，则此方法等效于 TryEnter。

Note

用于 Monitor 锁定对象（即引用类型），而不是值类型。 有关详细信息，请参阅 Monitor 类主题。

为了确保线程未进入关键节，应检查方法的返回值，并在关键节中执行代码（仅当其返回值为 true时）。 以下代码片段显示了用于调用此方法的模式。 请注意，应在块中finally调用Exit，以确保调用线程在发生异常时释放关键节上的锁。

var lockObj = new Object();
var timeout = TimeSpan.FromMilliseconds(500);

if (Monitor.TryEnter(lockObj, timeout)) {
   try {
      // The critical section.
   }
   finally {
      // Ensure that the lock is released.
      Monitor.Exit(lockObj);
   }
}
else {
   // The lock was not acquired.
}

Dim lockObj As New Object()
Dim timeout = TimeSpan.FromMilliseconds(500)

If Monitor.TryEnter(lockObj, timeout) Then
   Try
      ' The critical section.
   Finally
      ' Ensure that the lock is released.
      Monitor.Exit(lockObj)
   End Try
Else
   ' The lock was not acquired.
End If

另请参阅

适用于

TryEnter(Object, Boolean)

Source:
Monitor.CoreCLR.cs
Source:
Monitor.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs

尝试获取指定对象的排他锁，并原子地设置一个值，该值指示是否已获取锁。

public:
 static void TryEnter(System::Object ^ obj, bool % lockTaken);
public static void TryEnter(object obj, ref bool lockTaken);
static member TryEnter : obj * bool -> unit
Public Shared Sub TryEnter (obj As Object, ByRef lockTaken As Boolean)

参数

obj
Object

要在其上获取锁的对象。

lockTaken
Boolean

尝试获取锁的结果，由引用传递。 输入必须是 false。 输出是 true 如果获取锁，则输出为 ;否则，输出为 false。 即使尝试获取锁期间发生异常，也会设置输出。

例外

ArgumentException

要输入 lockTaken 的为 true.

ArgumentNullException

参数 obj 为 null.

示例

以下代码显示了使用 TryEnter(Object, Boolean) 方法重载的基本模式。 此重载始终设置传递给 ref 参数 （ByRef in Visual Basic） lockTaken 的变量的值，即使该方法引发异常，变量的值也是测试锁是否必须释放的可靠方法。

bool acquiredLock = false;

try
{
    Monitor.TryEnter(lockObject, ref acquiredLock);
    if (acquiredLock)
    {

        // Code that accesses resources that are protected by the lock.
    }
    else
    {
    
        // Code to deal with the fact that the lock was not acquired.
    }
}
finally
{
    if (acquiredLock)
    {
        Monitor.Exit(lockObject);
    }
}

Dim acquiredLock As Boolean = False

Try
    Monitor.TryEnter(lockObject, acquiredLock)
    If acquiredLock Then

        ' Code that accesses resources that are protected by the lock.

    Else

        ' Code to deal with the fact that the lock was not acquired.

    End If
Finally
    If acquiredLock Then
        Monitor.Exit(lockObject)
    End If
End Try

注解

如果成功，此方法将获取参数的 obj 排他锁。 无论锁是否可用，此方法都会立即返回。

如果未因为引发异常而锁定，则为 lockTaken 参数指定的变量在 false 此方法结束后。 这允许程序在所有情况下确定是否有必要释放锁。

此方法类似于 Enter(Object, Boolean)，但它永远不会阻止当前线程。 如果线程在未阻止的情况下无法输入，则 lockTaken 参数设置为 false 方法返回时。

Note

用于 Monitor 锁定对象（即引用类型），而不是值类型。 有关详细信息，请参阅文章 Monitor 。

若要确保线程未进入关键节，应仅在关键节的值 lockTaken 为时检查并执行关键节中的代码的值 true。 以下代码片段显示了用于调用此方法的模式。 请注意，应在块中finally调用Exit，以确保调用线程在发生异常时释放关键节上的锁。

var lockObj = new Object();
bool lockTaken = false;

try {
   Monitor.TryEnter(lockObj, ref lockTaken); 
   if (lockTaken) {
      // The critical section.
   }
   else {
      // The lock was not acquired.
   }
}
finally {
   // Ensure that the lock is released.
   if (lockTaken) {
      Monitor.Exit(lockObj);
   }
}

Dim lockObj As New Object()
Dim lockTaken As Boolean = False

Try 
   Monitor.TryEnter(lockObj, lockTaken) 
   If lockTaken Then
      ' The critical section.
   Else 
      ' The lock was not acquired.
   End If
Finally 
   ' Ensure that the lock is released.
   If lockTaken Then Monitor.Exit(lockObj)
End Try

适用于

TryEnter(Object)

Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs

尝试获取指定对象的排他锁。

public:
 static bool TryEnter(System::Object ^ obj);
public static bool TryEnter(object obj);
static member TryEnter : obj -> bool
Public Shared Function TryEnter (obj As Object) As Boolean

参数

obj
Object

要在其上获取锁的对象。

返回

Boolean

true 如果当前线程获取锁，则为否则，为 false.

例外

ArgumentNullException

参数 obj 为 null.

示例

下面的代码示例演示如何使用 TryEnter 该方法。

using System;
using System.Threading;
using System.Collections.Generic;
using System.Text;

class SafeQueue<T>
{
   // A queue that is protected by Monitor.
   private Queue<T> m_inputQueue = new Queue<T>();

   // Lock the queue and add an element.
   public void Enqueue(T qValue)
   {
      // Request the lock, and block until it is obtained.
      Monitor.Enter(m_inputQueue);
      try
      {
         // When the lock is obtained, add an element.
         m_inputQueue.Enqueue(qValue);
      }
      finally
      {
         // Ensure that the lock is released.
         Monitor.Exit(m_inputQueue);
      }
   }

   // Try to add an element to the queue: Add the element to the queue
   // only if the lock is immediately available.
   public bool TryEnqueue(T qValue)
   {
      // Request the lock.
      if (Monitor.TryEnter(m_inputQueue))
      {
         try
         {
            m_inputQueue.Enqueue(qValue);
         }
         finally
         {
            // Ensure that the lock is released.
            Monitor.Exit(m_inputQueue);
         }
         return true;
      }
      else
      {
         return false;
      }
   }

   // Try to add an element to the queue: Add the element to the queue
   // only if the lock becomes available during the specified time
   // interval.
   public bool TryEnqueue(T qValue, int waitTime)
   {
      // Request the lock.
      if (Monitor.TryEnter(m_inputQueue, waitTime))
      {
         try
         {
            m_inputQueue.Enqueue(qValue);
         }
         finally
         {
            // Ensure that the lock is released.
            Monitor.Exit(m_inputQueue);
         }
         return true;
      }
      else
      {
         return false;
      }
   }

   // Lock the queue and dequeue an element.
   public T Dequeue()
   {
      T retval;

      // Request the lock, and block until it is obtained.
      Monitor.Enter(m_inputQueue);
      try
      {
         // When the lock is obtained, dequeue an element.
         retval = m_inputQueue.Dequeue();
      }
      finally
      {
         // Ensure that the lock is released.
         Monitor.Exit(m_inputQueue);
      }

      return retval;
   }

   // Delete all elements that equal the given object.
   public int Remove(T qValue)
   {
      int removedCt = 0;

      // Wait until the lock is available and lock the queue.
      Monitor.Enter(m_inputQueue);
      try
      {
         int counter = m_inputQueue.Count;
         while (counter > 0)
            // Check each element.
         {
            T elem = m_inputQueue.Dequeue();
            if (!elem.Equals(qValue))
            {
               m_inputQueue.Enqueue(elem);
            }
            else
            {
               // Keep a count of items removed.
               removedCt += 1;
            }
            counter = counter - 1;
         }
      }
      finally
      {
         // Ensure that the lock is released.
         Monitor.Exit(m_inputQueue);
      }

      return removedCt;
   }

   // Print all queue elements.
   public string PrintAllElements()
   {
      StringBuilder output = new StringBuilder();

      // Lock the queue.
      Monitor.Enter(m_inputQueue);
      try
      {
         foreach( T elem in m_inputQueue )
         {
            // Print the next element.
            output.AppendLine(elem.ToString());
         }
      }
      finally
      {
         // Ensure that the lock is released.
         Monitor.Exit(m_inputQueue);
      }

      return output.ToString();
   }
}

public class Example
{
   private static SafeQueue<int> q = new SafeQueue<int>();
   private static int threadsRunning = 0;
   private static int[][] results = new int[3][];

   static void Main()
   {
      Console.WriteLine("Working...");

      for(int i = 0; i < 3; i++)
      {
         Thread t = new Thread(ThreadProc);
         t.Start(i);
         Interlocked.Increment(ref threadsRunning);
      }
   }

   private static void ThreadProc(object state)
   {
      DateTime finish = DateTime.Now.AddSeconds(10);
      Random rand = new Random();
      int[] result = { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
      int threadNum = (int) state;

      while (DateTime.Now < finish)

      {
         int what = rand.Next(250);
         int how = rand.Next(100);

         if (how < 16)
         {
            q.Enqueue(what);
            result[(int)ThreadResultIndex.EnqueueCt] += 1;
         }
         else if (how < 32)
         {
            if (q.TryEnqueue(what))
            {
               result[(int)ThreadResultIndex.TryEnqueueSucceedCt] += 1;
            }
            else
            {
               result[(int)ThreadResultIndex.TryEnqueueFailCt] += 1;
            }
         }
         else if (how < 48)
         {
            // Even a very small wait significantly increases the success
            // rate of the conditional enqueue operation.
            if (q.TryEnqueue(what, 10))
            {
               result[(int)ThreadResultIndex.TryEnqueueWaitSucceedCt] += 1;
            }
            else
            {
               result[(int)ThreadResultIndex.TryEnqueueWaitFailCt] += 1;
            }
         }
         else if (how < 96)
         {
            result[(int)ThreadResultIndex.DequeueCt] += 1;
            try
            {
               q.Dequeue();
            }
            catch
            {
               result[(int)ThreadResultIndex.DequeueExCt] += 1;
            }
         }
         else
         {
            result[(int)ThreadResultIndex.RemoveCt] += 1;
            result[(int)ThreadResultIndex.RemovedCt] += q.Remove(what);
         }
      }

      results[threadNum] = result;

      if (0 == Interlocked.Decrement(ref threadsRunning))
      {
         StringBuilder sb = new StringBuilder(
            "                               Thread 1 Thread 2 Thread 3    Total\n");

         for(int row = 0; row < 9; row++)
         {
            int total = 0;
            sb.Append(titles[row]);

            for(int col = 0; col < 3; col++)
            {
               sb.Append(String.Format("{0,9}", results[col][row]));
               total += results[col][row];
            }

            sb.AppendLine(String.Format("{0,9}", total));
         }

         Console.WriteLine(sb.ToString());
      }
   }

   private static string[] titles = {
      "Enqueue                       ",
      "TryEnqueue succeeded          ",
      "TryEnqueue failed             ",
      "TryEnqueue(T, wait) succeeded ",
      "TryEnqueue(T, wait) failed    ",
      "Dequeue attempts              ",
      "Dequeue exceptions            ",
      "Remove operations             ",
      "Queue elements removed        "};

   private enum ThreadResultIndex
   {
      EnqueueCt,
      TryEnqueueSucceedCt,
      TryEnqueueFailCt,
      TryEnqueueWaitSucceedCt,
      TryEnqueueWaitFailCt,
      DequeueCt,
      DequeueExCt,
      RemoveCt,
      RemovedCt
   };
}

/* This example produces output similar to the following:

Working...
                               Thread 1 Thread 2 Thread 3    Total
Enqueue                          277382   515209   308464  1101055
TryEnqueue succeeded             276873   514621   308099  1099593
TryEnqueue failed                   109      181      134      424
TryEnqueue(T, wait) succeeded    276913   514434   307607  1098954
TryEnqueue(T, wait) failed            2        0        0        2
Dequeue attempts                 830980  1544081   924164  3299225
Dequeue exceptions                12102    21589    13539    47230
Remove operations                 69550   129479    77351   276380
Queue elements removed            11957    22572    13043    47572
 */

Imports System.Threading
Imports System.Collections.Generic
Imports System.Text

Class SafeQueue(Of T)

   ' A queue that is protected by Monitor.
   Private m_inputQueue As New Queue(Of T)

   ' Lock the queue and add an element.
   Public Sub Enqueue(ByVal qValue As T)

      ' Request the lock, and block until it is obtained.
      Monitor.Enter(m_inputQueue)
      Try
         ' When the lock is obtained, add an element.
         m_inputQueue.Enqueue(qValue)

      Finally
         ' Ensure that the lock is released.
         Monitor.Exit(m_inputQueue)
      End Try
   End Sub

   ' Try to add an element to the queue: Add the element to the queue 
   ' only if the lock is immediately available.
   Public Function TryEnqueue(ByVal qValue As T) As Boolean

      ' Request the lock.
      If Monitor.TryEnter(m_inputQueue) Then
         Try
            m_inputQueue.Enqueue(qValue)

         Finally
            ' Ensure that the lock is released.
            Monitor.Exit(m_inputQueue)
         End Try
         Return True
      Else
         Return False
      End If
   End Function

   ' Try to add an element to the queue: Add the element to the queue 
   ' only if the lock becomes available during the specified time
   ' interval.
   Public Function TryEnqueue(ByVal qValue As T, ByVal waitTime As Integer) As Boolean

      ' Request the lock.
      If Monitor.TryEnter(m_inputQueue, waitTime) Then
         Try
            m_inputQueue.Enqueue(qValue)

         Finally
            ' Ensure that the lock is released.
            Monitor.Exit(m_inputQueue)
         End Try
         Return True
      Else
         Return False
      End If
   End Function

   ' Lock the queue and dequeue an element.
   Public Function Dequeue() As T

      Dim retval As T

      ' Request the lock, and block until it is obtained.
      Monitor.Enter(m_inputQueue)
      Try
         ' When the lock is obtained, dequeue an element.
         retval = m_inputQueue.Dequeue()

      Finally
         ' Ensure that the lock is released.
         Monitor.Exit(m_inputQueue)
      End Try

      Return retval
   End Function

   ' Delete all elements that equal the given object.
   Public Function Remove(ByVal qValue As T) As Integer

      Dim removedCt As Integer = 0

      ' Wait until the lock is available and lock the queue.
      Monitor.Enter(m_inputQueue)
      Try
         Dim counter As Integer = m_inputQueue.Count
         While (counter > 0)
            'Check each element.
            Dim elem As T = m_inputQueue.Dequeue()
            If Not elem.Equals(qValue) Then
               m_inputQueue.Enqueue(elem)
            Else
               ' Keep a count of items removed.
               removedCt += 1
            End If
            counter = counter - 1
         End While

      Finally
         ' Ensure that the lock is released.
         Monitor.Exit(m_inputQueue)
      End Try

      Return removedCt
   End Function

   ' Print all queue elements.
   Public Function PrintAllElements() As String

      Dim output As New StringBuilder()

      'Lock the queue.
      Monitor.Enter(m_inputQueue)
      Try
         For Each elem As T In m_inputQueue
            ' Print the next element.
            output.AppendLine(elem.ToString())
         Next

      Finally
         ' Ensure that the lock is released.
         Monitor.Exit(m_inputQueue)
      End Try

      Return output.ToString()
   End Function
End Class

Public Class Example

   Private Shared q As New SafeQueue(Of Integer)
   Private Shared threadsRunning As Integer = 0
   Private Shared results(2)() As Integer

   Friend Shared Sub Main()

      Console.WriteLine("Working...")

      For i As Integer = 0 To 2

         Dim t As New Thread(AddressOf ThreadProc)
         t.Start(i)
         Interlocked.Increment(threadsRunning)

      Next i

   End Sub

   Private Shared Sub ThreadProc(ByVal state As Object)

      Dim finish As DateTime = DateTime.Now.AddSeconds(10)
      Dim rand As New Random()
      Dim result() As Integer = { 0, 0, 0, 0, 0, 0, 0, 0, 0 }
      Dim threadNum As Integer = CInt(state)

      While (DateTime.Now < finish)

         Dim what As Integer = rand.Next(250)
         Dim how As Integer = rand.Next(100)

         If how < 16 Then
            q.Enqueue(what)
            result(ThreadResultIndex.EnqueueCt) += 1
         Else If how < 32 Then
            If q.TryEnqueue(what)
               result(ThreadResultIndex.TryEnqueueSucceedCt) += 1
            Else
               result(ThreadResultIndex.TryEnqueueFailCt) += 1
            End If
         Else If how < 48 Then
            ' Even a very small wait significantly increases the success 
            ' rate of the conditional enqueue operation.
            If q.TryEnqueue(what, 10)
               result(ThreadResultIndex.TryEnqueueWaitSucceedCt) += 1
            Else
               result(ThreadResultIndex.TryEnqueueWaitFailCt) += 1
            End If
         Else If how < 96 Then
            result(ThreadResultIndex.DequeueCt) += 1
            Try
               q.Dequeue()
            Catch
               result(ThreadResultIndex.DequeueExCt) += 1
            End Try
         Else
            result(ThreadResultIndex.RemoveCt) += 1
            result(ThreadResultIndex.RemovedCt) += q.Remove(what)
         End If
         
      End While

      results(threadNum) = result

      If 0 = Interlocked.Decrement(threadsRunning) Then
      
         Dim sb As New StringBuilder( _
            "                               Thread 1 Thread 2 Thread 3    Total" & vbLf)

         For row As Integer = 0 To 8

            Dim total As Integer = 0
            sb.Append(titles(row))

            For col As Integer = 0 To 2

               sb.Append(String.Format("{0,9}", results(col)(row)))
               total += results(col)(row)

            Next col

            sb.AppendLine(String.Format("{0,9}", total))

         Next row

         Console.WriteLine(sb.ToString())

      End If     
    
   End Sub

   Private Shared titles() As String = { _
      "Enqueue                       ", _
      "TryEnqueue succeeded          ", _
      "TryEnqueue failed             ", _
      "TryEnqueue(T, wait) succeeded ", _
      "TryEnqueue(T, wait) failed    ", _
      "Dequeue attempts              ", _
      "Dequeue exceptions            ", _
      "Remove operations             ", _
      "Queue elements removed        "  _
   }

   Private Enum ThreadResultIndex
      EnqueueCt
      TryEnqueueSucceedCt
      TryEnqueueFailCt
      TryEnqueueWaitSucceedCt
      TryEnqueueWaitFailCt
      DequeueCt
      DequeueExCt
      RemoveCt
      RemovedCt
   End Enum

End Class

' This example produces output similar to the following:
'
'Working...
'                               Thread 1 Thread 2 Thread 3    Total
'Enqueue                          294357   512164   302838  1109359
'TryEnqueue succeeded             294486   512403   303117  1110006
'TryEnqueue failed                   108      234      127      469
'TryEnqueue(T, wait) succeeded    294259   512796   302556  1109611
'TryEnqueue(T, wait) failed            1        1        1        3
'Dequeue attempts                 882266  1537993   907795  3328054
'Dequeue exceptions                12691    21474    13480    47645
'Remove operations                 74059   128715    76187   278961
'Queue elements removed            12667    22606    13219    48492

注解

如果成功，此方法将获取参数的 obj 排他锁。 无论锁是否可用，此方法都会立即返回。

此方法类似于 Enter，但它永远不会阻止当前线程。 如果线程在未阻塞的情况下无法输入，该方法将 false,返回。

Note

用于 Monitor 锁定对象（即引用类型），而不是值类型。 有关详细信息，请参阅文章 Monitor 。

为了确保线程未进入关键节，应检查方法的返回值，并在关键节中执行代码（仅当其返回值为 true时）。 以下代码片段显示了用于调用此方法的模式。 请注意，应在块中finally调用Exit，以确保调用线程在发生异常时释放关键节上的锁。

var lockObj = new Object();

if (Monitor.TryEnter(lockObj)) {
   try {
      // The critical section.
   }
   finally {
      // Ensure that the lock is released.
      Monitor.Exit(lockObj);
   }
}
else {
   // The lock was not axquired.
}

Dim lockObj As New Object()

If Monitor.TryEnter(lockObj) Then
   Try
      ' The critical section.
   Finally
      ' Ensure that the lock is released.
      Monitor.Exit(lockObj)
   End Try
Else
   ' The lock was not acquired.
End If

另请参阅

适用于

TryEnter(Object, Int32)

Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs
Source:
Monitor.CoreCLR.cs

尝试获取指定对象上的排他锁的指定毫秒数。

public:
 static bool TryEnter(System::Object ^ obj, int millisecondsTimeout);
public static bool TryEnter(object obj, int millisecondsTimeout);
static member TryEnter : obj * int -> bool
Public Shared Function TryEnter (obj As Object, millisecondsTimeout As Integer) As Boolean

参数

obj
Object

要在其上获取锁的对象。

millisecondsTimeout
Int32

等待锁的毫秒数。

返回

Boolean

true 如果当前线程获取锁，则为否则，为 false.

例外

ArgumentNullException

参数 obj 为 null.

ArgumentOutOfRangeException

millisecondsTimeout 为负数，且不等于 Infinite。

注解

millisecondsTimeout如果参数相等Infinite，则此方法等效Enter于 。 如果 millisecondsTimeout 等于 0，则此方法等效于 TryEnter。

Note

用于 Monitor 锁定对象（即引用类型），而不是值类型。 有关详细信息，请参阅文章 Monitor 。

为了确保线程未进入关键节，应检查方法的返回值，并在关键节中执行代码（仅当其返回值为 true时）。 以下代码片段显示了用于调用此方法的模式。 请注意，应在块中finally调用Exit，以确保调用线程在发生异常时释放关键节上的锁。

var lockObj = new Object();
int timeout = 500;

if (Monitor.TryEnter(lockObj, timeout)) {
   try {
      // The critical section.
   }
   finally {
      // Ensure that the lock is released.
      Monitor.Exit(lockObj);
   }
}
else {
   // The lock was not acquired.
}

Dim lockObj As New Object()
Dim timeout As Integer = 500

If Monitor.TryEnter(lockObj, timeout) Then
   Try
      ' The critical section.
   Finally
      ' Ensure that the lock is released.
      Monitor.Exit(lockObj)
   End Try
Else
   ' The lock was not acquired.
End If

另请参阅

适用于