Waits for any of the elements in the specified array to receive a signal, using a TimeSpan to specify the time interval and specifying whether to exit the synchronization domain before the wait.
public:
static int WaitAny(cli::array <System::Threading::WaitHandle ^> ^ waitHandles, TimeSpan timeout, bool exitContext);public static int WaitAny(System.Threading.WaitHandle[] waitHandles, TimeSpan timeout, bool exitContext);static member WaitAny : System.Threading.WaitHandle[] * TimeSpan * bool -> intPublic Shared Function WaitAny (waitHandles As WaitHandle(), timeout As TimeSpan, exitContext As Boolean) As IntegerA WaitHandle array containing the objects for which the current instance will wait.
A TimeSpan that represents the number of milliseconds to wait, or a TimeSpan that represents -1 milliseconds to wait indefinitely.
true to exit the synchronization domain for the context before the wait (if in a synchronized context), and reacquire it afterward; otherwise, false.
The array index of the object that satisfied the wait, or WaitTimeout if no object satisfied the wait and a time interval equivalent to timeout has passed.
The waitHandles parameter is null.
-or-
One or more of the objects in the waitHandles array is null.
The number of objects in waitHandles is greater than the system permits.
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 completed because a thread exited without releasing a mutex.
waitHandles is an array with no elements, and the .NET Framework version is 2.0 or later.
The waitHandles array contains a transparent proxy for a WaitHandle in another application domain.
The following code example demonstrates how to use the thread pool to simultaneously search for a file on multiple disks. For space considerations, only the root directory of each disk is searched.
using System;
using System.IO;
using System.Threading;
class Test
{
static void Main()
{
Search search = new Search();
search.FindFile("SomeFile.dat");
}
}
class Search
{
// Maintain state information to pass to FindCallback.
class State
{
public AutoResetEvent autoEvent;
public string fileName;
public State(AutoResetEvent autoEvent, string fileName)
{
this.autoEvent = autoEvent;
this.fileName = fileName;
}
}
AutoResetEvent[] autoEvents;
String[] diskLetters;
public Search()
{
// Retrieve an array of disk letters.
diskLetters = Environment.GetLogicalDrives();
autoEvents = new AutoResetEvent[diskLetters.Length];
for(int i = 0; i < diskLetters.Length; i++)
{
autoEvents[i] = new AutoResetEvent(false);
}
}
// Search for fileName in the root directory of all disks.
public void FindFile(string fileName)
{
for(int i = 0; i < diskLetters.Length; i++)
{
Console.WriteLine("Searching for {0} on {1}.",
fileName, diskLetters[i]);
ThreadPool.QueueUserWorkItem(
new WaitCallback(FindCallback),
new State(autoEvents[i], diskLetters[i] + fileName));
}
// Wait for the first instance of the file to be found.
int index = WaitHandle.WaitAny(
autoEvents, new TimeSpan(0, 0, 3), false);
if(index == WaitHandle.WaitTimeout)
{
Console.WriteLine("\n{0} not found.", fileName);
}
else
{
Console.WriteLine("\n{0} found on {1}.", fileName,
diskLetters[index]);
}
}
// Search for stateInfo.fileName.
void FindCallback(object state)
{
State stateInfo = (State)state;
// Signal if the file is found.
if(File.Exists(stateInfo.fileName))
{
stateInfo.autoEvent.Set();
}
}
}
Imports System.IO
Imports System.Threading
Public Class Test
<MTAThread> _
Shared Sub Main()
Dim search As New Search()
search.FindFile("SomeFile.dat")
End Sub
End Class
Public Class Search
' Maintain state information to pass to FindCallback.
Class State
Public autoEvent As AutoResetEvent
Public fileName As String
Sub New(anEvent As AutoResetEvent, fName As String)
autoEvent = anEvent
fileName = fName
End Sub
End Class
Dim autoEvents() As AutoResetEvent
Dim diskLetters() As String
Sub New()
' Retrieve an array of disk letters.
diskLetters = Environment.GetLogicalDrives()
autoEvents = New AutoResetEvent(diskLetters.Length - 1) {}
For i As Integer = 0 To diskLetters.Length - 1
autoEvents(i) = New AutoResetEvent(False)
Next i
End Sub
' Search for fileName in the root directory of all disks.
Sub FindFile(fileName As String)
For i As Integer = 0 To diskLetters.Length - 1
Console.WriteLine("Searching for {0} on {1}.", _
fileName, diskLetters(i))
ThreadPool.QueueUserWorkItem(AddressOf FindCallback, _
New State(autoEvents(i), diskLetters(i) & fileName))
Next i
' Wait for the first instance of the file to be found.
Dim index As Integer = WaitHandle.WaitAny( _
autoEvents, New TimeSpan(0, 0, 3), False)
If index = WaitHandle.WaitTimeout
Console.WriteLine(vbCrLf & "{0} not found.", fileName)
Else
Console.WriteLine(vbCrLf & "{0} found on {1}.", _
fileName, diskLetters(index))
End If
End Sub
' Search for stateInfo.fileName.
Sub FindCallback(state As Object)
Dim stateInfo As State = DirectCast(state, State)
' Signal if the file is found.
If File.Exists(stateInfo.fileName) Then
stateInfo.autoEvent.Set()
End If
End Sub
End Class
If timeout is zero, the method does not block. It tests the state of the wait handles and returns immediately.
The WaitAny method throws an AbandonedMutexException only when the wait completes because of an abandoned mutex. If waitHandles contains a released mutex with a lower index number than the abandoned mutex, the WaitAny method completes normally and the exception is not 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.
This method returns when the wait terminates, either when any of the handles are signaled or when a time-out occurs. If more than one object becomes signaled during the call, the return value is the array index of the signaled object with the smallest index value of all the signaled objects.
The maximum number of the wait handles is 64, and 63 if the current thread is in STA state.
The maximum value for timeout is Int32.MaxValue.
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.
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