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SafeFileHandle Class


Represents a wrapper class for a file handle.

Namespace:   Microsoft.Win32.SafeHandles
Assembly:  mscorlib (in mscorlib.dll)

public sealed class SafeFileHandle : SafeHandleZeroOrMinusOneIsInvalid

System_CAPS_pubmethodSafeFileHandle(IntPtr, Boolean)

Initializes a new instance of the SafeFileHandle class.


Gets a value indicating whether the handle is closed.(Inherited from SafeHandle.)


Gets a value that indicates whether the handle is invalid.(Inherited from SafeHandleZeroOrMinusOneIsInvalid.)


Marks the handle for releasing and freeing resources.(Inherited from SafeHandle.)


Manually increments the reference counter on SafeHandle instances.(Inherited from SafeHandle.)


Returns the value of the handle field.(Inherited from SafeHandle.)


Manually decrements the reference counter on a SafeHandle instance.(Inherited from SafeHandle.)


Releases all resources used by the SafeHandle class.(Inherited from SafeHandle.)


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Serves as the default hash function. (Inherited from Object.)


Gets the Type of the current instance.(Inherited from Object.)


Marks a handle as no longer used.(Inherited from SafeHandle.)


Returns a string that represents the current object.(Inherited from Object.)

This class is derived from SafeHandleZeroOrMinusOneIsInvalid. A value of 0 or -1 is an invalid file handle.


This type implements the IDisposable interface. When you have finished using the type, you should dispose of it either directly or indirectly. To dispose of the type directly, call its Dispose method in a try/catch block. To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). For more information, see the “Using an Object that Implements IDisposable” section in the IDisposable interface topic.

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()

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

        catch (Exception e)


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)

    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)

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




requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

Universal Windows Platform
Available since 10
.NET Framework
Available since 2.0

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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