WaitHandle.WaitAll Method

Definition

Waits for all the elements in the specified array to receive a signal.

Overloads

WaitAll(WaitHandle[], TimeSpan, Boolean)

Waits for all the elements in the specified array to receive a signal, using a TimeSpan value to specify the time interval, and specifying whether to exit the synchronization domain before the wait.

WaitAll(WaitHandle[], Int32, Boolean)

Waits for all the elements in the specified array to receive a signal, using an Int32 value to specify the time interval and specifying whether to exit the synchronization domain before the wait.

WaitAll(WaitHandle[], TimeSpan)

Waits for all the elements in the specified array to receive a signal, using a TimeSpan value to specify the time interval.

WaitAll(WaitHandle[], Int32)

Waits for all the elements in the specified array to receive a signal, using an Int32 value to specify the time interval.

WaitAll(WaitHandle[])

Waits for all the elements in the specified array to receive a signal.

WaitAll(WaitHandle[], TimeSpan, Boolean)

Source:
WaitHandle.cs
Source:
WaitHandle.cs
Source:
WaitHandle.cs

Waits for all the elements in the specified array to receive a signal, using a TimeSpan value to specify the time interval, and specifying whether to exit the synchronization domain before the wait.

public static bool WaitAll (System.Threading.WaitHandle[] waitHandles, TimeSpan timeout, bool exitContext);

Parameters

waitHandles
WaitHandle[]

A WaitHandle array containing the objects for which the current instance will wait. This array cannot contain multiple references to the same object.

timeout
TimeSpan

A TimeSpan that represents the number of milliseconds to wait, or a TimeSpan that represents -1 milliseconds, to wait indefinitely.

exitContext
Boolean

true to exit the synchronization domain for the context before the wait (if in a synchronized context), and reacquire it afterward; otherwise, false.

Returns

true when every element in waitHandles has received a signal; otherwise false.

Exceptions

The waitHandles parameter is null.

-or-

One or more of the objects in the waitHandles array is null.

-or-

waitHandles is an array with no elements and the .NET Framework version is 2.0 or later.

The waitHandles array contains elements that are duplicates.

The number of objects in waitHandles is greater than the system permits.

-or-

The STAThreadAttribute attribute is applied to the thread procedure for the current thread, and waitHandles contains more than one element.

waitHandles is an array with no elements and the .NET Framework version is 1.0 or 1.1.

timeout is a negative number other than -1 milliseconds, which represents an infinite time-out.

-or-

timeout is greater than Int32.MaxValue.

The wait terminated because a thread exited without releasing a mutex.

The waitHandles array contains a transparent proxy for a WaitHandle in another application domain.

Examples

The following code example shows how to use the thread pool to asynchronously create and write to a group of files. Each write operation is queued as a work item and signals when it is finished. The main thread waits for all the items to signal and then exits.

using System;
using System.IO;
using System.Security.Permissions;
using System.Threading;

class Test
{
    static void Main()
    {
        const int numberOfFiles = 5;
        string dirName = @"C:\TestTest";
        string fileName;

        byte[] byteArray;
        Random randomGenerator = new Random();

        ManualResetEvent[] manualEvents = 
            new ManualResetEvent[numberOfFiles];
        State stateInfo;

        if(!Directory.Exists(dirName))
        {
            Directory.CreateDirectory(dirName);
        }

        // Queue the work items that create and write to the files.
        for(int i = 0; i < numberOfFiles; i++)
        {
            fileName = string.Concat(
                dirName, @"\Test", i.ToString(), ".dat");

            // Create random data to write to the file.
            byteArray = new byte[1000000];
            randomGenerator.NextBytes(byteArray);

            manualEvents[i] = new ManualResetEvent(false);

            stateInfo = 
                new State(fileName, byteArray, manualEvents[i]);

            ThreadPool.QueueUserWorkItem(new WaitCallback(
                Writer.WriteToFile), stateInfo);
        }
    
        // Since ThreadPool threads are background threads, 
        // wait for the work items to signal before exiting.
        if(WaitHandle.WaitAll(
            manualEvents, new TimeSpan(0, 0, 5), false))
        {
            Console.WriteLine("Files written - main exiting.");
        }
        else
        {
            // The wait operation times out.
            Console.WriteLine("Error writing files - main exiting.");
        }
    }
}

// Maintain state to pass to WriteToFile.
class State
{
    public string fileName;
    public byte[] byteArray;
    public ManualResetEvent manualEvent;

    public State(string fileName, byte[] byteArray, 
        ManualResetEvent manualEvent)
    {
        this.fileName = fileName;
        this.byteArray = byteArray;
        this.manualEvent = manualEvent;
    }
}

class Writer
{
    static int workItemCount = 0;
    Writer() {}

    public static void WriteToFile(object state)
    {
        int workItemNumber = workItemCount;
        Interlocked.Increment(ref workItemCount);
        Console.WriteLine("Starting work item {0}.",
            workItemNumber.ToString());
        State stateInfo = (State)state;
        FileStream fileWriter = null;

        // Create and write to the file.
        try
        {
            fileWriter = new FileStream(
                stateInfo.fileName, FileMode.Create);
            fileWriter.Write(stateInfo.byteArray, 
                0, stateInfo.byteArray.Length);
        }
        finally
        {
            if(fileWriter != null)
            {
                fileWriter.Close();
            }

            // Signal Main that the work item has finished.
            Console.WriteLine("Ending work item {0}.", 
                workItemNumber.ToString());
            stateInfo.manualEvent.Set();
        }
    }
}

Remarks

If timeout is zero, the method does not block. It tests the state of the wait handles and returns immediately.

If a mutex is abandoned, an AbandonedMutexException is thrown. An abandoned mutex often indicates a serious coding error. In the case of a system-wide mutex, it might indicate that an application has been terminated abruptly (for example, by using Windows Task Manager). The exception contains information useful for debugging.

The WaitAll method returns when the wait terminates, which means either all the handles are signaled or a time-out occurs. If more than 64 handles are passed, a NotSupportedException is thrown. If the array contains duplicates, the call will fail.

Note

The WaitAll method is not supported on threads in STA state.

The maximum value for timeout is Int32.MaxValue.

Exiting the context

The exitContext parameter has no effect unless this method is called from inside a nondefault managed context. The managed context can be nondefault if your thread is inside a call to an instance of a class derived from ContextBoundObject. Even if you're currently executing a method on a class that isn't derived from ContextBoundObject, like String, you can be in a nondefault context if a ContextBoundObject is on your stack in the current application domain.

When your code is executing in a nondefault context, specifying true for exitContext causes the thread to exit the nondefault managed context (that is, to transition to the default context) before executing this method. The thread returns to the original nondefault context after the call to this method completes.

Exiting the context can be useful when the context-bound class has the SynchronizationAttribute attribute. In that case, all calls to members of the class are automatically synchronized, and the synchronization domain is the entire body of code for the class. If code in the call stack of a member calls this method and specifies true for exitContext, the thread exits the synchronization domain, which allows a thread that's blocked on a call to any member of the object to proceed. When this method returns, the thread that made the call must wait to reenter the synchronization domain.

Applies to

.NET 9 and other versions
Product Versions
.NET Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1

WaitAll(WaitHandle[], Int32, Boolean)

Source:
WaitHandle.cs
Source:
WaitHandle.cs
Source:
WaitHandle.cs

Waits for all the elements in the specified array to receive a signal, using an Int32 value to specify the time interval and specifying whether to exit the synchronization domain before the wait.

public static bool WaitAll (System.Threading.WaitHandle[] waitHandles, int millisecondsTimeout, bool exitContext);

Parameters

waitHandles
WaitHandle[]

A WaitHandle array containing the objects for which the current instance will wait. This array cannot contain multiple references to the same object (duplicates).

millisecondsTimeout
Int32

The number of milliseconds to wait, or Infinite (-1) to wait indefinitely.

exitContext
Boolean

true to exit the synchronization domain for the context before the wait (if in a synchronized context), and reacquire it afterward; otherwise, false.

Returns

true when every element in waitHandles has received a signal; otherwise, false.

Exceptions

The waitHandles parameter is null.

-or-

One or more of the objects in the waitHandles array is null.

-or-

waitHandles is an array with no elements and the .NET Framework version is 2.0 or later.

The waitHandles array contains elements that are duplicates.

The number of objects in waitHandles is greater than the system permits.

-or-

The current thread is in STA state, and waitHandles contains more than one element.

waitHandles is an array with no elements and the .NET Framework version is 1.0 or 1.1.

millisecondsTimeout is a negative number other than -1, which represents an infinite time-out.

The wait completed because a thread exited without releasing a mutex.

The waitHandles array contains a transparent proxy for a WaitHandle in another application domain.

Examples

The following code example shows how to use the thread pool to asynchronously create and write to a group of files. Each write operation is queued as a work item and signals when it is finished. The main thread waits for all the items to signal and then exits.

using System;
using System.IO;
using System.Security.Permissions;
using System.Threading;

class Test
{
    static void Main()
    {
        const int numberOfFiles = 5;
        string dirName = @"C:\TestTest";
        string fileName;

        byte[] byteArray;
        Random randomGenerator = new Random();

        ManualResetEvent[] manualEvents = 
            new ManualResetEvent[numberOfFiles];
        State stateInfo;

        if(!Directory.Exists(dirName))
        {
            Directory.CreateDirectory(dirName);
        }

        // Queue the work items that create and write to the files.
        for(int i = 0; i < numberOfFiles; i++)
        {
            fileName = string.Concat(
                dirName, @"\Test", i.ToString(), ".dat");

            // Create random data to write to the file.
            byteArray = new byte[1000000];
            randomGenerator.NextBytes(byteArray);

            manualEvents[i] = new ManualResetEvent(false);

            stateInfo = 
                new State(fileName, byteArray, manualEvents[i]);

            ThreadPool.QueueUserWorkItem(new WaitCallback(
                Writer.WriteToFile), stateInfo);
        }
    
        // Since ThreadPool threads are background threads, 
        // wait for the work items to signal before exiting.
        if(WaitHandle.WaitAll(manualEvents, 5000, false))
        {
            Console.WriteLine("Files written - main exiting.");
        }
        else
        {
            // The wait operation times out.
            Console.WriteLine("Error writing files - main exiting.");
        }
    }
}

// Maintain state to pass to WriteToFile.
class State
{
    public string fileName;
    public byte[] byteArray;
    public ManualResetEvent manualEvent;

    public State(string fileName, byte[] byteArray, 
        ManualResetEvent manualEvent)
    {
        this.fileName = fileName;
        this.byteArray = byteArray;
        this.manualEvent = manualEvent;
    }
}

class Writer
{
    static int workItemCount = 0;
    Writer() {}

    public static void WriteToFile(object state)
    {
        int workItemNumber = workItemCount;
        Interlocked.Increment(ref workItemCount);
        Console.WriteLine("Starting work item {0}.",
            workItemNumber.ToString());
        State stateInfo = (State)state;
        FileStream fileWriter = null;

        // Create and write to the file.
        try
        {
            fileWriter = new FileStream(
                stateInfo.fileName, FileMode.Create);
            fileWriter.Write(stateInfo.byteArray, 
                0, stateInfo.byteArray.Length);
        }
        finally
        {
            if(fileWriter != null)
            {
                fileWriter.Close();
            }

            // Signal Main that the work item has finished.
            Console.WriteLine("Ending work item {0}.", 
                workItemNumber.ToString());
            stateInfo.manualEvent.Set();
        }
    }
}

Remarks

If millisecondsTimeout is zero, the method does not block. It tests the state of the wait handles and returns immediately.

If a mutex is abandoned, an AbandonedMutexException is thrown. An abandoned mutex often indicates a serious coding error. In the case of a system-wide mutex, it might indicate that an application has been terminated abruptly (for example, by using Windows Task Manager). The exception contains information useful for debugging.

The WaitAll method returns when the wait terminates, which means either when all the handles are signaled or when time-out occurs. If more than 64 handles are passed, a NotSupportedException is thrown. If there are duplicates in the array, the call fails with a DuplicateWaitObjectException.

Note

The WaitAll method is not supported on threads in STA state.

Exiting the context

The exitContext parameter has no effect unless this method is called from inside a nondefault managed context. The managed context can be nondefault if your thread is inside a call to an instance of a class derived from ContextBoundObject. Even if you're currently executing a method on a class that isn't derived from ContextBoundObject, like String, you can be in a nondefault context if a ContextBoundObject is on your stack in the current application domain.

When your code is executing in a nondefault context, specifying true for exitContext causes the thread to exit the nondefault managed context (that is, to transition to the default context) before executing this method. The thread returns to the original nondefault context after the call to this method completes.

Exiting the context can be useful when the context-bound class has the SynchronizationAttribute attribute. In that case, all calls to members of the class are automatically synchronized, and the synchronization domain is the entire body of code for the class. If code in the call stack of a member calls this method and specifies true for exitContext, the thread exits the synchronization domain, which allows a thread that's blocked on a call to any member of the object to proceed. When this method returns, the thread that made the call must wait to reenter the synchronization domain.

Applies to

.NET 9 and other versions
Product Versions
.NET Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1

WaitAll(WaitHandle[], TimeSpan)

Source:
WaitHandle.cs
Source:
WaitHandle.cs
Source:
WaitHandle.cs

Waits for all the elements in the specified array to receive a signal, using a TimeSpan value to specify the time interval.

public static bool WaitAll (System.Threading.WaitHandle[] waitHandles, TimeSpan timeout);

Parameters

waitHandles
WaitHandle[]

A WaitHandle array containing the objects for which the current instance will wait. This array cannot contain multiple references to the same object.

timeout
TimeSpan

A TimeSpan that represents the number of milliseconds to wait, or a TimeSpan that represents -1 milliseconds, to wait indefinitely.

Returns

true when every element in waitHandles has received a signal; otherwise, false.

Exceptions

The waitHandles parameter is null.

-or-

One or more of the objects in the waitHandles array is null.

-or-

waitHandles is an array with no elements.

The waitHandles array contains elements that are duplicates.

Note: In the .NET for Windows Store apps or the Portable Class Library, catch the base class exception, ArgumentException, instead.

The number of objects in waitHandles is greater than the system permits.

-or-

The current thread is in STA state, and waitHandles contains more than one element.

timeout is a negative number other than -1 milliseconds, which represents an infinite time-out.

-or-

timeout is greater than Int32.MaxValue.

The wait terminated because a thread exited without releasing a mutex.

The waitHandles array contains a transparent proxy for a WaitHandle in another application domain.

Remarks

If timeout is zero, the method does not block. It tests the state of the wait handles and returns immediately.

The WaitAll method returns when the wait terminates, which means either all the handles are signaled or a time-out occurs. If more than 64 handles are passed, a NotSupportedException is thrown. If the array contains duplicates, the call will fail.

Note

The WaitAll method is not supported on threads in STA state.

The maximum value for timeout is Int32.MaxValue.

Calling this method overload is the same as calling the WaitAll(WaitHandle[], TimeSpan, Boolean) overload and specifying false for exitContext.

Applies to

.NET 9 and other versions
Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1
UWP 10.0

WaitAll(WaitHandle[], Int32)

Source:
WaitHandle.cs
Source:
WaitHandle.cs
Source:
WaitHandle.cs

Waits for all the elements in the specified array to receive a signal, using an Int32 value to specify the time interval.

public static bool WaitAll (System.Threading.WaitHandle[] waitHandles, int millisecondsTimeout);

Parameters

waitHandles
WaitHandle[]

A WaitHandle array containing the objects for which the current instance will wait. This array cannot contain multiple references to the same object (duplicates).

millisecondsTimeout
Int32

The number of milliseconds to wait, or Infinite (-1) to wait indefinitely.

Returns

true when every element in waitHandles has received a signal; otherwise, false.

Exceptions

The waitHandles parameter is null.

-or-

One or more of the objects in the waitHandles array is null.

-or-

waitHandles is an array with no elements.

The waitHandles array contains elements that are duplicates.

Note: In the .NET for Windows Store apps or the Portable Class Library, catch the base class exception, ArgumentException, instead.

The number of objects in waitHandles is greater than the system permits.

-or-

The current thread is in STA state, and waitHandles contains more than one element.

millisecondsTimeout is a negative number other than -1, which represents an infinite time-out.

The wait completed because a thread exited without releasing a mutex.

The waitHandles array contains a transparent proxy for a WaitHandle in another application domain.

Remarks

If millisecondsTimeout is zero, the method does not block. It tests the state of the wait handles and returns immediately.

The WaitAll method returns when the wait terminates, which means either when all the handles are signaled or when time-out occurs. If more than 64 handles are passed, a NotSupportedException is thrown. If there are duplicates in the array, the call fails with a DuplicateWaitObjectException.

Note

The WaitAll method is not supported on threads in STA state.

Calling this method overload is the same as calling the WaitAll(WaitHandle[], Int32, Boolean) overload and specifying false for exitContext.

Applies to

.NET 9 and other versions
Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1
UWP 10.0

WaitAll(WaitHandle[])

Source:
WaitHandle.cs
Source:
WaitHandle.cs
Source:
WaitHandle.cs

Waits for all the elements in the specified array to receive a signal.

public static bool WaitAll (System.Threading.WaitHandle[] waitHandles);

Parameters

waitHandles
WaitHandle[]

A WaitHandle array containing the objects for which the current instance will wait. This array cannot contain multiple references to the same object.

Returns

true when every element in waitHandles has received a signal; otherwise the method never returns.

Exceptions

The waitHandles parameter is null. -or-

One or more of the objects in the waitHandles array are null.

-or-

waitHandles is an array with no elements and the .NET Framework version is 2.0 or later.

The waitHandles array contains elements that are duplicates.

Note: In the .NET for Windows Store apps or the Portable Class Library, catch the base class exception, ArgumentException, instead.

The number of objects in waitHandles is greater than the system permits.

-or-

The current thread is in STA state, and waitHandles contains more than one element.

waitHandles is an array with no elements and the .NET Framework version is 1.0 or 1.1.

The wait terminated because a thread exited without releasing a mutex.

The waitHandles array contains a transparent proxy for a WaitHandle in another application domain.

Examples

The following code example shows how to use the thread pool to asynchronously create and write to a group of files. Each write operation is queued as a work item and signals when it is finished. The main thread waits for all the items to signal and then exits.

using System;
using System.IO;
using System.Security.Permissions;
using System.Threading;

class Test
{
    static void Main()
    {
        const int numberOfFiles = 5;
        string dirName = @"C:\TestTest";
        string fileName;

        byte[] byteArray;
        Random randomGenerator = new Random();

        ManualResetEvent[] manualEvents = 
            new ManualResetEvent[numberOfFiles];
        State stateInfo;

        if(!Directory.Exists(dirName))
        {
            Directory.CreateDirectory(dirName);
        }

        // Queue the work items that create and write to the files.
        for(int i = 0; i < numberOfFiles; i++)
        {
            fileName = string.Concat(
                dirName, @"\Test", i.ToString(), ".dat");

            // Create random data to write to the file.
            byteArray = new byte[1000000];
            randomGenerator.NextBytes(byteArray);

            manualEvents[i] = new ManualResetEvent(false);

            stateInfo = 
                new State(fileName, byteArray, manualEvents[i]);

            ThreadPool.QueueUserWorkItem(new WaitCallback(
                Writer.WriteToFile), stateInfo);
        }
    
        // Since ThreadPool threads are background threads, 
        // wait for the work items to signal before exiting.
        WaitHandle.WaitAll(manualEvents);
        Console.WriteLine("Files written - main exiting.");
    }
}

// Maintain state to pass to WriteToFile.
class State
{
    public string fileName;
    public byte[] byteArray;
    public ManualResetEvent manualEvent;

    public State(string fileName, byte[] byteArray, 
        ManualResetEvent manualEvent)
    {
        this.fileName = fileName;
        this.byteArray = byteArray;
        this.manualEvent = manualEvent;
    }
}

class Writer
{
    static int workItemCount = 0;
    Writer() {}

    public static void WriteToFile(object state)
    {
        int workItemNumber = workItemCount;
        Interlocked.Increment(ref workItemCount);
        Console.WriteLine("Starting work item {0}.",
            workItemNumber.ToString());
        State stateInfo = (State)state;
        FileStream fileWriter = null;

        // Create and write to the file.
        try
        {
            fileWriter = new FileStream(
                stateInfo.fileName, FileMode.Create);
            fileWriter.Write(stateInfo.byteArray, 
                0, stateInfo.byteArray.Length);
        }
        finally
        {
            if(fileWriter != null)
            {
                fileWriter.Close();
            }

            // Signal Main that the work item has finished.
            Console.WriteLine("Ending work item {0}.", 
                workItemNumber.ToString());
            stateInfo.manualEvent.Set();
        }
    }
}

Remarks

AbandonedMutexException is new in the .NET Framework version 2.0. In previous versions, the WaitAll method returns true when a mutex is abandoned. An abandoned mutex often indicates a serious coding error. In the case of a system-wide mutex, it might indicate that an application has been terminated abruptly (for example, by using Windows Task Manager). The exception contains information useful for debugging.

The WaitAll method returns when all the handles are signaled. If more than 64 handles are passed, a NotSupportedException is thrown. If the array contains duplicates, the call fails with a DuplicateWaitObjectException.

Note

The WaitAll method is not supported on threads in STA state.

Calling this method overload is equivalent to calling the WaitAll(WaitHandle[], Int32, Boolean) method overload and specifying -1 (or Timeout.Infinite) for millisecondsTimeout and true for exitContext.

Applies to

.NET 9 and other versions
Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1
UWP 10.0