SafeFileHandle SafeFileHandle SafeFileHandle SafeFileHandle Class

定義

代表檔案控制代碼的包裝函式類別。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
繼承
屬性

範例

下列程式碼範例示範如何開啟檔案,使用SafeFileHandle類別和未受管理CreateFile函式。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

備註

此類別衍生自 SafeHandleZeroOrMinusOneIsInvalidThis class is derived from SafeHandleZeroOrMinusOneIsInvalid. 0 或-1 的值是無效的檔案控制代碼。A value of 0 or -1 is an invalid file handle.

重要

此類型會實作IDisposable介面。This type implements the IDisposable interface. 當您完成使用型別時,您應該處置它直接或間接。When you have finished using the type, you should dispose of it either directly or indirectly. 若要直接處置型別,呼叫其Dispose方法中的try / catch區塊。To dispose of the type directly, call its Dispose method in a try/catch block. 若要處置它間接,使用的語言建構這類using(在 C# 中) 或Using(在 Visual Basic)。To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). 如需詳細資訊,請參閱 「 使用物件,實作 IDisposable 」 一節IDisposable介面 > 主題。For more information, see the "Using an Object that Implements IDisposable" section in the IDisposable interface topic.

建構函式

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

初始化 SafeFileHandle 類別的新執行個體。Initializes a new instance of the SafeFileHandle class.

屬性

IsClosed IsClosed IsClosed IsClosed

取得值,指出控制代碼是否已關閉。Gets a value indicating whether the handle is closed.

(Inherited from SafeHandle)
IsInvalid IsInvalid IsInvalid IsInvalid

取得值,這個值表示控制代碼是否無效。Gets a value that indicates whether the handle is invalid.

方法

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

標記要釋出和釋放資源的控制代碼。Marks the handle for releasing and freeing resources.

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

手動遞增 SafeHandle 執行個體上的參考計數器。Manually increments the reference counter on SafeHandle instances.

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

傳回 handle 欄位的值。Returns the value of the handle field.

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

手動遞減 SafeHandle 執行個體上的參考計數器。Manually decrements the reference counter on a SafeHandle instance.

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

釋放 SafeHandle 類別所使用的所有資源。Releases all resources used by the SafeHandle class.

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

釋放 SafeHandle 類別所使用的 Unmanaged 資源,指定是否要執行一般處置 (Dispose) 作業。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)

判斷指定的物件是否等於目前的物件。Determines whether the specified object is equal to the current object.

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

做為預設雜湊函式。Serves as the default hash function.

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

取得目前執行個體的 TypeGets the Type of the current instance.

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

建立目前 Object 的淺層複本 (Shallow Copy)。Creates a shallow copy of the current Object.

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

在衍生類別中覆寫時,執行釋放控制代碼所需的程式碼。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)

將控制代碼設定為指定的既有控制代碼。Sets the handle to the specified pre-existing handle.

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

將控制代碼標記為不再使用。Marks a handle as no longer used.

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

傳回代表目前物件的字串。Returns a string that represents the current object.

(Inherited from Object)

欄位

handle handle handle handle

指定要包裝的控制代碼。Specifies the handle to be wrapped.

(Inherited from SafeHandle)

安全性

SecurityCriticalAttribute
需要完全信任立即呼叫端。requires full trust for the immediate caller. 此成員不能由部分信任或不透明的程式碼。This member cannot be used by partially trusted or transparent code.

適用於

另請參閱