SafeWaitHandle Constructors

Definition

Namespace:

Microsoft.Win32.SafeHandles

Assembly:

System.Runtime.dll

Overloads

SafeWaitHandle()	Creates a SafeWaitHandle.
SafeWaitHandle(IntPtr, Boolean)	Initializes a new instance of the SafeWaitHandle class.

SafeWaitHandle()

Source:

SafeWaitHandle.cs

Creates a SafeWaitHandle.

public:
 SafeWaitHandle();

public SafeWaitHandle ();

Public Sub New ()

SafeWaitHandle(IntPtr, Boolean)

Source:

SafeWaitHandle.cs

Initializes a new instance of the SafeWaitHandle class.

public:
 SafeWaitHandle(IntPtr existingHandle, bool ownsHandle);

public SafeWaitHandle (IntPtr existingHandle, bool ownsHandle);

new Microsoft.Win32.SafeHandles.SafeWaitHandle : nativeint * bool -> Microsoft.Win32.SafeHandles.SafeWaitHandle

Public Sub New (existingHandle As IntPtr, ownsHandle As Boolean)

Parameters

existingHandle

IntPtr

nativeint

An IntPtr object that represents the pre-existing handle to use.

ownsHandle

Boolean

true to reliably release the handle during the finalization phase; false to prevent reliable release (not recommended).

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 UnmanagedMutex("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.");
        }

        Console.ReadLine();
    }
}

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)]
    static extern IntPtr CreateMutex(IntPtr lpMutexAttributes, bool bInitialOwner,
   string lpName);

    [DllImport("kernel32.dll")]
    public static extern bool ReleaseMutex(SafeWaitHandle hMutex);

    private SafeWaitHandle handleValue = null;
    private IntPtr mutexAttrValue = IntPtr.Zero;
    private string nameValue = null;

    public UnmanagedMutex(string Name)
    {
        nameValue = Name;
    }

    public void Create()
    {
        if (nameValue == null && nameValue.Length == 0)
        {
            throw new ArgumentNullException("nameValue");
        }

         IntPtr ptr = CreateMutex(mutexAttrValue,
                                        true, nameValue);

         handleValue = new SafeWaitHandle(ptr, true);

         // 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 the handle is valid,
            // return it.
            if (!handleValue.IsInvalid)
            {
                return handleValue;
            }
            else
            {
                return null;
            }
        }
    }

    public string Name
    {
        get
        {
            return 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 IntPtr

    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

        Dim ptr As IntPtr = CreateMutex(mutexAttrValue, True, nameValue)

        handleValue = New SafeWaitHandle(ptr, True)

        ' 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

See also

• SafeHandleZeroOrMinusOneIsInvalid
• SafeHandle