Some C# .NET and DX

private static SlimDX.Direct3D9.Direct3D _direct3D9 = new SlimDX.Direct3D9.Direct3D();
private static Dictionary<IntPtr, SlimDX.Direct3D9.Device> _direct3DDeviceCache = new Dictionary<IntPtr, SlimDX.Direct3D9.Device>();

private SlimDX.Direct3D9.AdapterCollection _adaptersInfo = _direct3D9.Adapters;

--------------------

// Executed from Timer
private void DeskCapture()
{
    _GlobalVariables.var_hWnd = User32.GetWindowsHandle();

    Bitmap b;
    b = CaptureDXScreen(_GlobalVariables.var_hWnd);

    if (true)
        b.Save(@"_last_scr.jpg", ImageFormat.Jpeg);

    b.Dispose();

}

public static Bitmap CaptureDXScreen(IntPtr hWnd)
{
    Bitmap bitmap = null;

    SlimDX.Direct3D9.AdapterInformation adapterInfo = _direct3D9.Adapters[_GlobalVariables.SelectedDisplay];

    SlimDX.Direct3D9.Device device;

    int DisplayWidth = adapterInfo.CurrentDisplayMode.Width;
    int DisplayHeight = adapterInfo.CurrentDisplayMode.Height;

    #region Get Direct3D Device

    // Retrieve the existing Direct3D device if we already created one for the given handle
    if (_direct3DDeviceCache.ContainsKey(hWnd))
    {
        device = _direct3DDeviceCache[hWnd];
    }
    // We need to create a new device
    else
    {
        SlimDX.Direct3D9.PresentParameters presentParams = new SlimDX.Direct3D9.PresentParameters();

        presentParams.Windowed = true;
        presentParams.BackBufferCount = 1;
        presentParams.BackBufferFormat = adapterInfo.CurrentDisplayMode.Format;
        presentParams.BackBufferWidth = DisplayWidth;
        presentParams.BackBufferHeight = DisplayHeight;
        presentParams.SwapEffect = SlimDX.Direct3D9.SwapEffect.Flip;
        presentParams.DeviceWindowHandle = hWnd;
        presentParams.PresentationInterval = SlimDX.Direct3D9.PresentInterval.One;
        presentParams.FullScreenRefreshRateInHertz = 0;
        presentParams.PresentFlags = SlimDX.Direct3D9.PresentFlags.LockableBackBuffer; //Massive speed-up?
        //presentParams.PresentFlags = SlimDX.Direct3D9.PresentFlags.None;

        presentParams.EnableAutoDepthStencil = true;
        while (true)
        {
            presentParams.AutoDepthStencilFormat = SlimDX.Direct3D9.Format.D32;
            if (_direct3D9.CheckDeviceFormat(0, SlimDX.Direct3D9.DeviceType.Hardware, presentParams.BackBufferFormat, SlimDX.Direct3D9.Usage.DepthStencil, SlimDX.Direct3D9.ResourceType.Surface, presentParams.AutoDepthStencilFormat)) break;

            presentParams.AutoDepthStencilFormat = SlimDX.Direct3D9.Format.D24X8;
            if (_direct3D9.CheckDeviceFormat(0, SlimDX.Direct3D9.DeviceType.Hardware, presentParams.BackBufferFormat, SlimDX.Direct3D9.Usage.DepthStencil, SlimDX.Direct3D9.ResourceType.Surface, presentParams.AutoDepthStencilFormat)) break;

            presentParams.AutoDepthStencilFormat = SlimDX.Direct3D9.Format.D16;
            if (_direct3D9.CheckDeviceFormat(0, SlimDX.Direct3D9.DeviceType.Hardware, presentParams.BackBufferFormat, SlimDX.Direct3D9.Usage.DepthStencil, SlimDX.Direct3D9.ResourceType.Surface, presentParams.AutoDepthStencilFormat)) break;

            // Your graphics card does not support 16bit, 24bit nor 32bit depth stencil buffers!
        }

        device = new SlimDX.Direct3D9.Device(_direct3D9, adapterInfo.Adapter, SlimDX.Direct3D9.DeviceType.Hardware, hWnd, SlimDX.Direct3D9.CreateFlags.HardwareVertexProcessing, presentParams);
        _direct3DDeviceCache.Add(hWnd, device);

    }
    #endregion

    // Capture screen and copy the region into a Bitmap

    /* /* Method 1: GetFrontBufferData [!WORKS!] [!SLOWLY!]
        //------------------------------------------------------------
        //--NOTE--: While DWM is disabled and device.Adapter is >0 (not primary) than picture on grabbed surface is shifted in some direction by the width of primary screen
        //--------: *When DWM is enabled it works ok
        //------------------------------------------------------------
    using (SlimDX.Direct3D9.Surface surface = SlimDX.Direct3D9.Surface.CreateOffscreenPlain(device, adapterInfo.CurrentDisplayMode.Width, adapterInfo.CurrentDisplayMode.Height, SlimDX.Direct3D9.Format.A8R8G8B8, SlimDX.Direct3D9.Pool.SystemMemory))
    {
        device.GetFrontBufferData(0, surface);
        bitmap = new Bitmap(SlimDX.Direct3D9.Surface.ToStream(surface, SlimDX.Direct3D9.ImageFileFormat.Bmp, new Rectangle(0, 0, DisplayWidth, DisplayHeight)));
    }
    // */


    //* /* Method 2: GetBackBuffer [!DOES NOT WORK!] [!FASTER?!]
        //------------------------------------------------------------
        //--NOTE--: Output picture is black. DWM no matters I guess...
        //------------------------------------------------------------
    int _width = DisplayWidth/_GlobalVariables.var_ScreenDivide;
    int _height = DisplayHeight / _GlobalVariables.var_ScreenDivide;

    Surface _renderTarget = null;

    using (Surface backBuffer = device.GetBackBuffer(0, 0))
    {
        Surface.ToFile(backBuffer, "__m2_backbuffer.jpg", ImageFileFormat.Jpg);
        /// First Get Render Target, so we know the exactly size of the surface
        Surface renderTargetTemp = device.GetRenderTarget(0);

        // Create our Surface
        _renderTarget = Surface.CreateRenderTarget(device, _width, _height, renderTargetTemp.Description.Format, MultisampleType.None, 0, false);
        // Resize from Render Surface to Our Surface || src,dest
        device.StretchRectangle(renderTargetTemp, _renderTarget, TextureFilter.None);
        // Get Render Data
        renderTargetTemp = _renderTarget;

        // Create offscreen surface to use as copy of render target data
        _renderTarget = Surface.CreateOffscreenPlain(device, _width, _height, renderTargetTemp.Description.Format, Pool.SystemMemory);

        // copies renderTarget data from device memory to system memory || src,dest
        device.GetRenderTargetData(renderTargetTemp, _renderTarget);

        // And release our surface
        renderTargetTemp.Dispose();

        //enkel als debug:
        Surface.ToFile(_renderTarget, "_m2_surface.jpg", ImageFileFormat.Jpg);

        bitmap = new Bitmap(SlimDX.Direct3D9.Surface.ToStream(_renderTarget, SlimDX.Direct3D9.ImageFileFormat.Bmp, new Rectangle(0, 0, _width, _height)));
    }
    // */

    /* /* Method 3: GetBackBuffer [!DOES NOT WORK!] [!FASTER?!]
        //------------------------------------------------------------
        //--NOTE--: Output picture is black. DWM no matters I guess...
        //------------------------------------------------------------
    using (SlimDX.Direct3D9.Surface surface = device.GetRenderTarget(0))
    {
        Surface.ToFile(surface, "_m3_ss1.jpg", ImageFileFormat.Jpg);
        using (SlimDX.Direct3D9.Surface surface2 = SlimDX.Direct3D9.Surface.CreateOffscreenPlain(device, surface.Description.Width, surface.Description.Height, surface.Description.Format, SlimDX.Direct3D9.Pool.SystemMemory))
        {
            Surface.ToFile(surface2, "_m3_ss2.jpg", ImageFileFormat.Jpg);
            device.GetRenderTargetData(surface, surface2);
            // You have to use client coordinates here
            bitmap = new Bitmap(SlimDX.Direct3D9.Surface.ToStream(surface2, SlimDX.Direct3D9.ImageFileFormat.Bmp, new Rectangle(0, 0, _width, _height)));
        }
    }
    // */

    return bitmap;

}