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POEject USB device via C#
 

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  1. POEject USB device via C#
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    <p>I was looking for a short way to eject USB-devices via C#-code, so I coded a little class myself, yet it simply doesn't work. Since there's no popup that says "Lock success!" I assume that the problem relies within the "LockVolume"-function, but I don't know where.</p> <p>Does anybody see the mistake I made?</p> <pre><code>class USBEject { [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)] private static extern IntPtr CreateFile( string lpFileName, uint dwDesiredAccess, uint dwShareMode, IntPtr SecurityAttributes, uint dwCreationDisposition, uint dwFlagsAndAttributes, IntPtr hTemplateFile ); [DllImport("kernel32.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)] private static extern bool DeviceIoControl( IntPtr hDevice, uint dwIoControlCode, IntPtr lpInBuffer, uint nInBufferSize, IntPtr lpOutBuffer, uint nOutBufferSize, out uint lpBytesReturned, IntPtr lpOverlapped ); [DllImport("kernel32.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)] private static extern bool DeviceIoControl( IntPtr hDevice, uint dwIoControlCode, byte[] lpInBuffer, uint nInBufferSize, IntPtr lpOutBuffer, uint nOutBufferSize, out uint lpBytesReturned, IntPtr lpOverlapped ); [DllImport("kernel32.dll", SetLastError = true)] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool CloseHandle(IntPtr hObject); private IntPtr handle = IntPtr.Zero; const int GENERIC_READ = 0x80000000; const int GENERIC_WRITE = 0x40000000; const int FILE_SHARE_READ = 0x1; const int FILE_SHARE_WRITE = 0x2; const int FSCTL_LOCK_VOLUME = 0x00090018; const int FSCTL_DISMOUNT_VOLUME = 0x00090020; const int IOCTL_STORAGE_EJECT_MEDIA = 0x2D4808; const int IOCTL_STORAGE_MEDIA_REMOVAL = 0x002D4804; /// &lt;summary&gt; /// Constructor for the USBEject class /// &lt;/summary&gt; /// &lt;param name="driveLetter"&gt;This should be the drive letter. Format: F:/, C:/..&lt;/param&gt; public USBEject(string driveLetter) { string filename = @"\\.\" + driveLetter[0] + ":"; handle = CreateFile(filename, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, IntPtr.Zero, 0x3, 0, IntPtr.Zero); } public bool Eject() { if (LockVolume(handle) &amp;&amp; DismountVolume(handle)) { PreventRemovalOfVolume(handle, false); return AutoEjectVolume(handle); } return false; } private bool LockVolume(IntPtr handle) { uint byteReturned; for (int i = 0; i &lt; 10; i++) { if (DeviceIoControl(handle, FSCTL_LOCK_VOLUME, IntPtr.Zero, 0, IntPtr.Zero, 0, out byteReturned, IntPtr.Zero)) { System.Windows.Forms.MessageBox.Show("Lock success!"); return true; } Thread.Sleep(500); } return false; } private bool PreventRemovalOfVolume(IntPtr handle, bool prevent) { byte[] buf = new byte[1]; uint retVal; buf[0] = (prevent) ? (byte)1 : (byte)0; return DeviceIoControl(handle, IOCTL_STORAGE_MEDIA_REMOVAL, buf, 1, IntPtr.Zero, 0, out retVal, IntPtr.Zero); } private bool DismountVolume(IntPtr handle) { uint byteReturned; return DeviceIoControl(handle, FSCTL_DISMOUNT_VOLUME, IntPtr.Zero, 0, IntPtr.Zero, 0, out byteReturned, IntPtr.Zero); } private bool AutoEjectVolume(IntPtr handle) { uint byteReturned; return DeviceIoControl(handle, IOCTL_STORAGE_EJECT_MEDIA, IntPtr.Zero, 0, IntPtr.Zero, 0, out byteReturned, IntPtr.Zero); } private bool CloseVolume(IntPtr handle) { return CloseHandle(handle); } } </code></pre>
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    1. COWhere API calls return a failure code, what error does [`GetLastError`](http://msdn.microsoft.com/en-us/library/ms679360(VS.85).aspx) return?
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    2. COLooks okay. Locking a volume is never not a problem. Ensure no process is using the drive letter, including Windows Explorer. And check if the Windows "Safely Remove Hardware" works.
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    3. COActually it seems that the CreateFile-function returns an invalid handle. This explains why locking the device fails, but why does CreateFile return an invalid handle?
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