C# Signature:

[DllImport("gdi32.dll")]
static extern int GetDeviceCaps(IntPtr hdc, int nIndex);

VB.NET Signature:

<DllImport("gdi32.dll")> _
Public Shared Function GetDeviceCaps(ByVal hDC As IntPtr, ByVal nIndex As Integer) As Integer
End Function

User-Defined Types:

You can use the following enumeration for passing in as nIndex:

public enum DeviceCap

    {
        /// <summary>
        /// Device driver version
        /// </summary>
        DRIVERVERSION = 0,
        /// <summary>
        /// Device classification
        /// </summary>
        TECHNOLOGY = 2,
        /// <summary>
        /// Horizontal size in millimeters
        /// </summary>
        HORZSIZE = 4,
        /// <summary>
        /// Vertical size in millimeters
        /// </summary>
        VERTSIZE = 6,
        /// <summary>
        /// Horizontal width in pixels
        /// </summary>
        HORZRES = 8,
        /// <summary>
        /// Vertical height in pixels
        /// </summary>
        VERTRES = 10,
        /// <summary>
        /// Number of bits per pixel
        /// </summary>
        BITSPIXEL = 12,
        /// <summary>
        /// Number of planes
        /// </summary>
        PLANES = 14,
        /// <summary>
        /// Number of brushes the device has
        /// </summary>
        NUMBRUSHES = 16,
        /// <summary>
        /// Number of pens the device has
        /// </summary>
        NUMPENS = 18,
        /// <summary>
        /// Number of markers the device has
        /// </summary>
        NUMMARKERS = 20,
        /// <summary>
        /// Number of fonts the device has
        /// </summary>
        NUMFONTS = 22,
        /// <summary>
        /// Number of colors the device supports
        /// </summary>
        NUMCOLORS = 24,
        /// <summary>
        /// Size required for device descriptor
        /// </summary>
        PDEVICESIZE = 26,
        /// <summary>
        /// Curve capabilities
        /// </summary>
        CURVECAPS = 28,
        /// <summary>
        /// Line capabilities
        /// </summary>
        LINECAPS = 30,
        /// <summary>
        /// Polygonal capabilities
        /// </summary>
        POLYGONALCAPS = 32,
        /// <summary>
        /// Text capabilities
        /// </summary>
        TEXTCAPS = 34,
        /// <summary>
        /// Clipping capabilities
        /// </summary>
        CLIPCAPS = 36,
        /// <summary>
        /// Bitblt capabilities
        /// </summary>
        RASTERCAPS = 38,
        /// <summary>
        /// Length of the X leg
        /// </summary>
        ASPECTX = 40,
        /// <summary>
        /// Length of the Y leg
        /// </summary>
        ASPECTY = 42,
        /// <summary>
        /// Length of the hypotenuse
        /// </summary>
        ASPECTXY = 44,
        /// <summary>
        /// Shading and Blending caps
        /// </summary>
        SHADEBLENDCAPS = 45,

        /// <summary>
        /// Logical pixels inch in X
        /// </summary>
        LOGPIXELSX = 88,
        /// <summary>
        /// Logical pixels inch in Y
        /// </summary>
        LOGPIXELSY = 90,

        /// <summary>
        /// Number of entries in physical palette
        /// </summary>
        SIZEPALETTE = 104,
        /// <summary>
        /// Number of reserved entries in palette
        /// </summary>
        NUMRESERVED = 106,
        /// <summary>
        /// Actual color resolution
        /// </summary>
        COLORRES = 108,

        // Printing related DeviceCaps. These replace the appropriate Escapes
        /// <summary>
        /// Physical Width in device units
        /// </summary>
        PHYSICALWIDTH = 110,
        /// <summary>
        /// Physical Height in device units
        /// </summary>
        PHYSICALHEIGHT = 111,
        /// <summary>
        /// Physical Printable Area x margin
        /// </summary>
        PHYSICALOFFSETX = 112,
        /// <summary>
        /// Physical Printable Area y margin
        /// </summary>
        PHYSICALOFFSETY = 113,
        /// <summary>
        /// Scaling factor x
        /// </summary>
        SCALINGFACTORX = 114,
        /// <summary>
        /// Scaling factor y
        /// </summary>
        SCALINGFACTORY = 115,

        /// <summary>
        /// Current vertical refresh rate of the display device (for displays only) in Hz
        /// </summary>
        VREFRESH = 116,
        /// <summary>
        /// Horizontal width of entire desktop in pixels
        /// </summary>
        DESKTOPVERTRES = 117,
        /// <summary>
        /// Vertical height of entire desktop in pixels
        /// </summary>
        DESKTOPHORZRES = 118,
        /// <summary>
        /// Preferred blt alignment
        /// </summary>
        BLTALIGNMENT = 119
    }

Notes:

None.

Tips & Tricks:

Please add some!

Sample Code:

Please add some!

Alternative Managed API:

System.Windows.Forms.Screen.PrimaryScreen might be of help in some cases. (Matt M Jacobsen)

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/devcons_88s3.asp

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