SafeWaitHandle Class
Represents a wrapper class for a wait handle.
Assembly: mscorlib (in mscorlib.dll)
The SafeWaitHandle class is used by the System.Threading.WaitHandle class. It is a wrapper for Win32 mutexes and auto and manual reset events.
The following code example demonstrates how to use interop to create a mutex using the SafeWaitHandle class and the unmanaged CreateMutex function.
Imports System Imports Microsoft.Win32.SafeHandles Imports System.Runtime.InteropServices Class SafeHandlesExample Shared Sub Main() Dim uMutex As New UnmanagedMutex("YourCompanyName_SafeHandlesExample_MUTEX") Try uMutex.Create() Console.WriteLine("Mutex created. Press Enter to release it.") Console.ReadLine() Catch e As Exception Console.WriteLine(e) Finally uMutex.Release() Console.WriteLine("Mutex Released.") End Try Console.ReadLine() End Sub End Class Class UnmanagedMutex ' Use interop to call the CreateMutex function. ' For more information about CreateMutex, ' see the unmanaged MSDN reference library. <DllImport("kernel32.dll", CharSet:=CharSet.Unicode)> _ Shared Function CreateMutex(ByVal lpMutexAttributes As IntPtr, ByVal bInitialOwner As Boolean, ByVal lpName As String) As SafeWaitHandle End Function ' Use interop to call the ReleaseMutex function. ' For more information about ReleaseMutex, ' see the unmanaged MSDN reference library. <DllImport("kernel32.dll")> _ Public Shared Function ReleaseMutex(ByVal hMutex As SafeWaitHandle) As Boolean End Function Private handleValue As SafeWaitHandle = Nothing Private mutexAttrValue As IntPtr = IntPtr.Zero Private nameValue As String = Nothing Public Sub New(ByVal Name As String) nameValue = Name End Sub Public Sub Create() If nameValue Is Nothing AndAlso nameValue.Length = 0 Then Throw New ArgumentNullException("nameValue") End If handleValue = CreateMutex(mutexAttrValue, True, nameValue) ' If the handle is invalid, ' get the last Win32 error ' and throw a Win32Exception. If handleValue.IsInvalid Then Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error()) End If End Sub Public ReadOnly Property Handle() As SafeWaitHandle Get ' If the handle is valid, ' return it. If Not handleValue.IsInvalid Then Return handleValue Else Return Nothing End If End Get End Property Public ReadOnly Property Name() As String Get Return nameValue End Get End Property Public Sub Release() ReleaseMutex(handleValue) End Sub End Class
- SecurityPermission
for permission to call unmanaged code. Demand value: LinkDemand. Associated enumeration: SecurityPermissionFlag.UnmanagedCode
System.Runtime.ConstrainedExecution.CriticalFinalizerObject
System.Runtime.InteropServices.SafeHandle
Microsoft.Win32.SafeHandles.SafeHandleZeroOrMinusOneIsInvalid
Microsoft.Win32.SafeHandles.SafeWaitHandle
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.