SafeFileHandle SafeFileHandle SafeFileHandle SafeFileHandle Class

Definição

Representa uma classe wrapper para um identificador de arquivo.Represents a wrapper class for a file handle.

public ref class SafeFileHandle sealed : Microsoft::Win32::SafeHandles::SafeHandleZeroOrMinusOneIsInvalid
[System.Security.SecurityCritical]
public sealed class SafeFileHandle : Microsoft.Win32.SafeHandles.SafeHandleZeroOrMinusOneIsInvalid
type SafeFileHandle = class
    inherit SafeHandleZeroOrMinusOneIsInvalid
Public NotInheritable Class SafeFileHandle
Inherits SafeHandleZeroOrMinusOneIsInvalid
Herança
Atributos

Exemplos

O exemplo de código a seguir demonstra como abrir um arquivo usando o SafeFileHandle classe e não gerenciado CreateFile função.The following code example demonstrates how to open a file using the SafeFileHandle class and the unmanaged CreateFile function.

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

class SafeHandlesExample
{

    static void Main()
    {
        try
        {

            UnmanagedFileLoader loader = new UnmanagedFileLoader("example.xml");


        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }
        Console.ReadLine();


    }
}

class UnmanagedFileLoader 
{

    public const short FILE_ATTRIBUTE_NORMAL = 0x80;
    public const short INVALID_HANDLE_VALUE = -1;
    public const uint GENERIC_READ = 0x80000000;
    public const uint GENERIC_WRITE = 0x40000000;
    public const uint CREATE_NEW = 1;
    public const uint CREATE_ALWAYS = 2;
    public const uint OPEN_EXISTING = 3;

    // Use interop to call the CreateFile function.
    // For more information about CreateFile,
    // see the unmanaged MSDN reference library.
    [DllImport("kernel32.dll", SetLastError = true, CharSet=CharSet.Unicode)]
    static extern SafeFileHandle CreateFile(string lpFileName, uint dwDesiredAccess,
      uint dwShareMode, IntPtr lpSecurityAttributes, uint dwCreationDisposition,
      uint dwFlagsAndAttributes, IntPtr hTemplateFile);



    private SafeFileHandle handleValue = null;


    public UnmanagedFileLoader(string Path)
    {
        Load(Path);
    }


    public void Load(string Path)
    {
        if (Path == null || Path.Length == 0)
        {
            throw new ArgumentNullException("Path");
        }

        // Try to open the file.
        handleValue = CreateFile(Path, GENERIC_WRITE, 0, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero);

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

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

    }

}
Imports System
Imports Microsoft.Win32.SafeHandles
Imports System.Runtime.InteropServices
Imports System.ComponentModel



Module SafeHandlesExample

    Sub Main()
        Try

            Dim loader As New UnmanagedFileLoader("example.xml")


        Catch e As Exception
            Console.WriteLine(e)
        End Try
        Console.ReadLine()

    End Sub
End Module



Class UnmanagedFileLoader


    Public Const FILE_ATTRIBUTE_NORMAL As Short = &H80
    Public Const INVALID_HANDLE_VALUE As Short = -1
    Public Const GENERIC_READ As Long = &H80000000
    Public Const GENERIC_WRITE As UInteger = &H40000000
    Public Const CREATE_NEW As UInteger = 1
    Public Const CREATE_ALWAYS As UInteger = 2
    Public Const OPEN_EXISTING As UInteger = 3


    ' Use interop to call the CreateFile function.
    ' For more information about CreateFile,
    ' see the unmanaged MSDN reference library.
    <DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Unicode)> _
    Private Shared Function CreateFile(ByVal lpFileName As String, ByVal dwDesiredAccess As System.UInt32, ByVal dwShareMode As System.UInt32, ByVal lpSecurityAttributes As IntPtr, ByVal dwCreationDisposition As System.UInt32, ByVal dwFlagsAndAttributes As System.UInt32, ByVal hTemplateFile As IntPtr) As Microsoft.Win32.SafeHandles.SafeFileHandle

    End Function


    Private handleValue As Microsoft.Win32.SafeHandles.SafeFileHandle = Nothing



    Public Sub New(ByVal Path As String)
        Load(Path)

    End Sub


    Public Sub Load(ByVal Path As String)
        If Path Is Nothing OrElse Path.Length = 0 Then
            Throw New ArgumentNullException("Path")
        End If

        ' Try to open the file.
        handleValue = CreateFile(Path, GENERIC_WRITE, 0, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero)

        ' 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 Microsoft.Win32.SafeHandles.SafeFileHandle
        Get
            ' If the handle is valid,
            ' return it.
            If Not handleValue.IsInvalid Then
                Return handleValue
            Else
                Return Nothing
            End If
        End Get
    End Property
End Class

Comentários

Essa classe é derivada de SafeHandleZeroOrMinusOneIsInvalid.This class is derived from SafeHandleZeroOrMinusOneIsInvalid. Um valor de 0 ou -1 é um identificador de arquivo inválido.A value of 0 or -1 is an invalid file handle.

Importante

Esse tipo implementa o IDisposable interface.This type implements the IDisposable interface. Quando você terminar de usar o tipo, você deve descartá-lo diretamente ou indiretamente.When you have finished using the type, you should dispose of it either directly or indirectly. Para descartar o tipo diretamente, chame seu Dispose método em um try / catch bloco.To dispose of the type directly, call its Dispose method in a try/catch block. Para descartá-los indiretamente, usar uma construção de linguagem, como using (em C#) ou Using (no Visual Basic).To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). Para obter mais informações, consulte a seção "Usando um objeto que implementa IDisposable" o IDisposable tópico da interface.For more information, see the "Using an Object that Implements IDisposable" section in the IDisposable interface topic.

Construtores

SafeFileHandle(IntPtr, Boolean) SafeFileHandle(IntPtr, Boolean) SafeFileHandle(IntPtr, Boolean) SafeFileHandle(IntPtr, Boolean)

Inicializa uma nova instância da classe SafeFileHandle.Initializes a new instance of the SafeFileHandle class.

Propriedades

IsClosed IsClosed IsClosed IsClosed

Obtém um valor que indica se o identificador está fechado.Gets a value indicating whether the handle is closed.

(Inherited from SafeHandle)
IsInvalid IsInvalid IsInvalid IsInvalid

Obtém um valor que indica se o identificador é inválido.Gets a value that indicates whether the handle is invalid.

Métodos

Close() Close() Close() Close()

Marca o identificador de liberação de recursos.Marks the handle for releasing and freeing resources.

(Inherited from SafeHandle)
DangerousAddRef(Boolean) DangerousAddRef(Boolean) DangerousAddRef(Boolean) DangerousAddRef(Boolean)

Incrementa manualmente o contador de referências em instâncias do SafeHandle.Manually increments the reference counter on SafeHandle instances.

(Inherited from SafeHandle)
DangerousGetHandle() DangerousGetHandle() DangerousGetHandle() DangerousGetHandle()

Retorna o valor do campo handle.Returns the value of the handle field.

(Inherited from SafeHandle)
DangerousRelease() DangerousRelease() DangerousRelease() DangerousRelease()

Diminui manualmente o contador de referência em uma instância SafeHandle.Manually decrements the reference counter on a SafeHandle instance.

(Inherited from SafeHandle)
Dispose() Dispose() Dispose() Dispose()

Libera todos os recursos usados pela classe SafeHandle.Releases all resources used by the SafeHandle class.

(Inherited from SafeHandle)
Dispose(Boolean) Dispose(Boolean) Dispose(Boolean) Dispose(Boolean)

Libera os recursos não gerenciados usados pela classe SafeHandle que especifica se deve executar uma operação de descarte normal.Releases the unmanaged resources used by the SafeHandle class specifying whether to perform a normal dispose operation.

(Inherited from SafeHandle)
Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determina se o objeto especificado é igual ao objeto atual.Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Serve como a função de hash padrão.Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Obtém o Type da instância atual.Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Cria uma cópia superficial do Object atual.Creates a shallow copy of the current Object.

(Inherited from Object)
ReleaseHandle() ReleaseHandle() ReleaseHandle() ReleaseHandle()

Quando substituído em uma classe derivada, executa o código necessário para liberar o identificador.When overridden in a derived class, executes the code required to free the handle.

(Inherited from SafeHandle)
SetHandle(IntPtr) SetHandle(IntPtr) SetHandle(IntPtr) SetHandle(IntPtr)

Define o identificador para o identificador pré-existente especificado.Sets the handle to the specified pre-existing handle.

(Inherited from SafeHandle)
SetHandleAsInvalid() SetHandleAsInvalid() SetHandleAsInvalid() SetHandleAsInvalid()

Marca um identificador como não mais usado.Marks a handle as no longer used.

(Inherited from SafeHandle)
ToString() ToString() ToString() ToString()

Retorna uma cadeia de caracteres que representa o objeto atual.Returns a string that represents the current object.

(Inherited from Object)

Campos

handle handle handle handle

Especifica o identificador a ser encapsulado.Specifies the handle to be wrapped.

(Inherited from SafeHandle)

Segurança

SecurityCriticalAttribute
requer confiança total para o chamador imediato.requires full trust for the immediate caller. Este membro não pode ser usado pelo código transparente ou parcialmente confiável.This member cannot be used by partially trusted or transparent code.

Aplica-se a

Veja também