SafeFileHandle SafeFileHandle SafeFileHandle SafeFileHandle Class

定义

表示文件句柄的包装类。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
继承
属性

示例

下面的代码示例演示如何使用SafeFileHandle类和非托管CreateFile函数来打开文件。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 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

注解

此类是从 SafeHandleZeroOrMinusOneIsInvalid 派生的。This class is derived from SafeHandleZeroOrMinusOneIsInvalid. 值0或-1 是无效的文件句柄。A value of 0 or -1 is an invalid file handle.

重要

此类型实现 IDisposable 接口。This type implements the IDisposable interface. 在使用完类型后,您应直接或间接释放类型。When you have finished using the type, you should dispose of it either directly or indirectly. 若要直接释放类型,请在 try/catch 块中调用其 Dispose 方法。To dispose of the type directly, call its Dispose method in a try/catch block. 若要间接释放类型,请使用 using(在 C# 中)或 Using(在 Visual Basic 中)等语言构造。To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). 有关详细信息,请参阅 IDisposable 接口主题中的“使用实现 IDisposable 的对象”一节。For more information, see the "Using an Object that Implements IDisposable" section in the IDisposable interface topic.

构造函数

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

初始化 SafeFileHandle 类的新实例。Initializes a new instance of the SafeFileHandle class.

属性

IsClosed IsClosed IsClosed IsClosed

获取一个值,该值指示句柄是否已关闭。Gets a value indicating whether the handle is closed.

(Inherited from SafeHandle)
IsInvalid IsInvalid IsInvalid IsInvalid

获取一个值,该值指示句柄是否无效。Gets a value that indicates whether the handle is invalid.

方法

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

标记句柄,以便释放资源。Marks the handle for releasing and freeing resources.

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

手动递增 SafeHandle 实例中的引用计数器。Manually increments the reference counter on SafeHandle instances.

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

返回 handle 字段的值。Returns the value of the handle field.

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

手动递减 SafeHandle 实例中的引用计数器。Manually decrements the reference counter on a SafeHandle instance.

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

释放 SafeHandle 类使用的所有资源。Releases all resources used by the SafeHandle class.

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

释放 SafeHandle 类所使用的非托管资源,并指定是否执行常规释放 (Dispose) 操作。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)

确定指定的对象是否等于当前对象。Determines whether the specified object is equal to the current object.

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

作为默认哈希函数。Serves as the default hash function.

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

获取当前实例的 TypeGets the Type of the current instance.

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

创建当前 Object 的浅表副本。Creates a shallow copy of the current Object.

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

如果在派生类中重写,执行释放句柄所需的代码。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)

将句柄设置为预先存在的指定句柄。Sets the handle to the specified pre-existing handle.

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

将句柄标记为不再使用。Marks a handle as no longer used.

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

返回表示当前对象的字符串。Returns a string that represents the current object.

(Inherited from Object)

字段

handle handle handle handle

指定要包装的句柄。Specifies the handle to be wrapped.

(Inherited from SafeHandle)

安全性

SecurityCriticalAttribute
需要对直接调用方的完全信任。requires full trust for the immediate caller. 部分受信任的或透明的代码不能使用此成员。This member cannot be used by partially trusted or transparent code.

适用于

另请参阅