This documentation is archived and is not being maintained.

SafeWaitHandle Class

Represents a wrapper class for a wait handle.

Namespace:  Microsoft.Win32.SafeHandles
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
<SecurityPermissionAttribute(SecurityAction.LinkDemand, UnmanagedCode := True)> _
Public NotInheritable Class SafeWaitHandle _
	Inherits SafeHandleZeroOrMinusOneIsInvalid
'Usage
Dim instance As SafeWaitHandle

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

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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.

.NET Framework

Supported in: 3.5, 3.0, 2.0
Show: