SafeWaitHandle Class

Definition

public ref class SafeWaitHandle sealed : System::Runtime::InteropServices::SafeHandle

public ref class SafeWaitHandle sealed : Microsoft::Win32::SafeHandles::SafeHandleZeroOrMinusOneIsInvalid

[System.Security.SecurityCritical]
public sealed class SafeWaitHandle : System.Runtime.InteropServices.SafeHandle

public sealed class SafeWaitHandle : Microsoft.Win32.SafeHandles.SafeHandleZeroOrMinusOneIsInvalid

[System.Security.SecurityCritical]
public sealed class SafeWaitHandle : Microsoft.Win32.SafeHandles.SafeHandleZeroOrMinusOneIsInvalid

[<System.Security.SecurityCritical>]
type SafeWaitHandle = class
 inherit SafeHandle

type SafeWaitHandle = class
 inherit SafeHandleZeroOrMinusOneIsInvalid

[<System.Security.SecurityCritical>]
type SafeWaitHandle = class
 inherit SafeHandleZeroOrMinusOneIsInvalid

Public NotInheritable Class SafeWaitHandle
Inherits SafeHandle

Public NotInheritable Class SafeWaitHandle
Inherits SafeHandleZeroOrMinusOneIsInvalid

Inheritance

Object

SafeHandle

SafeWaitHandle

Inheritance

Object

CriticalFinalizerObject

SafeHandle

SafeHandleZeroOrMinusOneIsInvalid

SafeWaitHandle

Attributes

SecurityCriticalAttribute

Examples

The following code example demonstrates how to use interop to create a mutex using the SafeWaitHandle class and the unmanaged CreateMutex function.

using System;
using Microsoft.Win32.SafeHandles;
using System.Runtime.InteropServices;

class SafeHandlesExample
{
 static void Main()
 {
 UnmanagedMutex uMutex = new("YourCompanyName_SafeHandlesExample_MUTEX");

 try
 {
 uMutex.Create();
 Console.WriteLine("Mutex created. Press Enter to release it.");
 Console.ReadLine();
 }
 catch (Exception e)
 {
 Console.WriteLine(e);
 }
 finally
 {
 uMutex.Release();
 Console.WriteLine("Mutex released.");
 }
 }
}

partial class UnmanagedMutex(string Name)
{
 // Use interop to call the CreateMutex function.
 [LibraryImport("kernel32.dll", EntryPoint = "CreateMutexW", StringMarshalling = StringMarshalling.Utf16)]
 private static partial SafeWaitHandle CreateMutex(
 IntPtr lpMutexAttributes,
 [MarshalAs(UnmanagedType.Bool)] bool bInitialOwner,
 string lpName
 );

 // Use interop to call the ReleaseMutex function.
 // For more information about ReleaseMutex,
 // see the unmanaged MSDN reference library.
 [LibraryImport("kernel32.dll")]
 [return: MarshalAs(UnmanagedType.Bool)]
 public static partial bool ReleaseMutex(SafeWaitHandle hMutex);

 private SafeWaitHandle _handleValue = null;
 private readonly IntPtr _mutexAttrValue = IntPtr.Zero;
 private string nameValue = Name;

 public void Create()
 {
 ArgumentException.ThrowIfNullOrEmpty(nameValue);

 _handleValue = CreateMutex(_mutexAttrValue,
 true, nameValue);

 // If the handle is invalid,
 // get the last Win32 error
 // and throw a Win32Exception.
 if (_handleValue.IsInvalid)
 {
 Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
 }
 }

 public SafeWaitHandle Handle
 {
 get
 {
 if (!_handleValue.IsInvalid)
 {
 return _handleValue;
 }
 else
 {
 return null;
 }
 }
 }

 public string Name => nameValue;

 public void Release()
 {
 ReleaseMutex(_handleValue);
 }
}

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

Remarks

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

See also

• SafeHandleZeroOrMinusOneIsInvalid
• WaitHandle
• Mutex
• AutoResetEvent
• ManualResetEvent