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SafeWaitHandle Class

Represents a wrapper class for a wait handle.


Namespace:  Microsoft.Win32.SafeHandles
Assemblies:   System.Runtime.Handles (in System.Runtime.Handles.dll)
  mscorlib (in mscorlib.dll)

Public NotInheritable Class SafeWaitHandle _
	Inherits SafeHandle

The SafeWaitHandle type exposes the following members.

Public methodSafeWaitHandleInitializes a new instance of the SafeWaitHandle class.

Public propertyIsClosedGets a value indicating whether the handle is closed. (Inherited from SafeHandle.)
Public propertyIsInvalidGets a value that indicates whether the handle is invalid. (Inherited from SafeHandleZeroOrMinusOneIsInvalid.)
Public propertyIsInvalid (Overrides SafeHandle.IsInvalid.)

Public methodCloseMarks the handle for releasing and freeing resources. (Inherited from SafeHandle.)
Public methodDangerousAddRefManually increments the reference counter on SafeHandle instances. (Inherited from SafeHandle.)
Public methodDangerousGetHandleReturns the value of the handle field. (Inherited from SafeHandle.)
Public methodDangerousReleaseManually decrements the reference counter on a SafeHandle instance. (Inherited from SafeHandle.)
Public methodDisposeReleases all resources used by the SafeHandle class. (Inherited from SafeHandle.)
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodSetHandleAsInvalidMarks a handle as no longer used. (Inherited from SafeHandle.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)

The SafeWaitHandle class is used by the System.Threading.WaitHandle class. It is a wrapper for Win32 mutexes and auto and manual reset events.

Important noteImportant

This type implements the IDisposable interface. When you have finished using the type, you should dispose of it either directly or indirectly. To dispose of the type directly, call its Dispose method in a try/catch block. To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). For more information, see the “Using an Object that Implements IDisposable” section in the IDisposable interface topic.

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")


            Console.WriteLine("Mutex created. Press Enter to release it.")

        Catch e As Exception
            Console.WriteLine("Mutex Released.")
        End Try


    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
        End If 

    End Sub 

    Public ReadOnly Property Handle() As SafeWaitHandle
            ' If the handle is valid, 
            ' return it. 
            If Not handleValue.IsInvalid Then 
                Return handleValue
                Return Nothing 
            End If 
        End Get 
    End Property 

    Public ReadOnly Property Name() As String 
            Return nameValue
        End Get 
    End Property 

    Public Sub Release()

    End Sub 
End Class

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

  • SecurityCriticalAttribute 

    requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

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