SafeFileHandle コンストラクタ
アセンブリ: mscorlib (mscorlib.dll 内)
構文
Dim preexistingHandle As IntPtr Dim ownsHandle As Boolean Dim instance As New SafeFileHandle(preexistingHandle, ownsHandle)
SafeFileHandle クラスおよび CreateFile アンマネージ関数を使用してファイルを開く方法のコード例を次に示します。
Imports System Imports Microsoft.Win32.SafeHandles Imports System.Runtime.InteropServices Imports System.ComponentModel Class SafeHandlesExample Shared Sub Main() Try Dim loader As New UnmanagedFileLoader("example.xml") Catch e As Exception Console.WriteLine(e) End Try Console.ReadLine() End Sub End Class 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)> _ 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 IntPtr End Function Private handleValue As SafeFileHandle = Nothing Public Sub New(ByVal Path As String) Load(Path) End Sub Public Sub Load(ByVal Path As String) If Path Is Nothing AndAlso Path.Length = 0 Then Throw New ArgumentNullException("Path") End If ' Try to open the file. Dim ptr As IntPtr = CreateFile(Path, GENERIC_WRITE, 0, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero) handleValue = New SafeFileHandle(ptr, True) ' If the handle is invalid, ' get the last Win32 error ' and throw a Win32Exception. If handleValue.IsInvalid Then Marshal.ThrowExceptionForHR(Marshal.GetLastWin32Error()) End If End Sub Public ReadOnly Property Handle() As 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
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)] static extern IntPtr 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. IntPtr ptr = CreateFile(Path, GENERIC_WRITE, 0, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero); handleValue = new SafeFileHandle(ptr, true); // If the handle is invalid, // get the last Win32 error // and throw a Win32Exception. if (handleValue.IsInvalid) { Marshal.ThrowExceptionForHR(Marshal.GetLastWin32Error()); } } public SafeFileHandle Handle { get { // If the handle is valid, // return it. if (!handleValue.IsInvalid) { return handleValue; } else { return null; } } } }
- SecurityPermission (アンマネージ コードを呼び出すために必要なアクセス許可)。 LinkDemand (セキュリティ アクション)。 UnmanagedCode (関連する列挙体)
Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。
参照
- SafeFileHandle コンストラクタのページへのリンク