SafeNativeMethods.cs

using System;
using System.Runtime.InteropServices;

namespace Magic.Samples.DisplaySettings
{
    static class SafeNativeMethods
    {
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
        public struct DEVMODE
        {
            // You can define the following constant
            // but OUTSIDE the structure because you know
            // that size and layout of the structure is very important
            // CCHDEVICENAME = 32 = 0x50
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
            public string dmDeviceName;
            // In addition you can define the last character array
            // as following:
            //[MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
            //public Char[] dmDeviceName;

            // After the 32-bytes array
            [MarshalAs(UnmanagedType.U2)]
            public UInt16 dmSpecVersion;

            [MarshalAs(UnmanagedType.U2)]
            public UInt16 dmDriverVersion;

            [MarshalAs(UnmanagedType.U2)]
            public UInt16 dmSize;

            [MarshalAs(UnmanagedType.U2)]
            public UInt16 dmDriverExtra;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmFields;

            public POINTL dmPosition;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmDisplayOrientation;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmDisplayFixedOutput;

            [MarshalAs(UnmanagedType.I2)]
            public Int16 dmColor;

            [MarshalAs(UnmanagedType.I2)]
            public Int16 dmDuplex;

            [MarshalAs(UnmanagedType.I2)]
            public Int16 dmYResolution;

            [MarshalAs(UnmanagedType.I2)]
            public Int16 dmTTOption;

            [MarshalAs(UnmanagedType.I2)]
            public Int16 dmCollate;

            // CCHDEVICENAME = 32 = 0x50
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
            public string dmFormName;
            // Also can be defined as
            //[MarshalAs(UnmanagedType.ByValArray, 
            //    SizeConst = 32, ArraySubType = UnmanagedType.U1)]
            //public Byte[] dmFormName;

            [MarshalAs(UnmanagedType.U2)]
            public UInt16 dmLogPixels;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmBitsPerPel;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmPelsWidth;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmPelsHeight;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmDisplayFlags;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmDisplayFrequency;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmICMMethod;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmICMIntent;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmMediaType;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmDitherType;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmReserved1;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmReserved2;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmPanningWidth;

            [MarshalAs(UnmanagedType.U4)]
            public UInt32 dmPanningHeight;

            /// <summary>
            /// Initializes the structure variables.
            /// </summary>
            public void Initialize()
            {
                this.dmDeviceName = new string(new char[32]);
                this.dmFormName = new string(new char[32]);
                this.dmSize = (ushort)Marshal.SizeOf(this);
            }
        }

        // 8-bytes structure
        [StructLayout(LayoutKind.Sequential)]
        public struct POINTL
        {
            public Int32 x;
            public Int32 y;
        }



        [DllImport("User32.dll", SetLastError = true, BestFitMapping = false, ThrowOnUnmappableChar = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern Boolean EnumDisplaySettings(
            [param: MarshalAs(UnmanagedType.LPTStr)]
            String lpszDeviceName,  // display device
            [param: MarshalAs(UnmanagedType.U4)]
            Int32 iModeNum,         // graphics mode
            [In, Out]
            ref DEVMODE lpDevMode       // graphics mode settings
            );

        public const int ENUM_CURRENT_SETTINGS = -1;
        public const int DMDO_DEFAULT = 0;
        public const int DMDO_90 = 1;
        public const int DMDO_180 = 2;
        public const int DMDO_270 = 3;



        [DllImport("User32.dll", SetLastError = true, BestFitMapping = false, ThrowOnUnmappableChar = true)]
        [return: MarshalAs(UnmanagedType.I4)]
        public static extern int ChangeDisplaySettings(
            [In, Out]
            ref DEVMODE lpDevMode,
            [param: MarshalAs(UnmanagedType.U4)]
            uint dwflags);



        [DllImport("kernel32.dll", SetLastError = true, BestFitMapping = false, ThrowOnUnmappableChar = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern uint FormatMessage(
            [param: MarshalAs(UnmanagedType.U4)]
            uint dwFlags,
            [param: MarshalAs(UnmanagedType.U4)]
            uint lpSource,
            [param: MarshalAs(UnmanagedType.U4)]
            uint dwMessageId,
            [param: MarshalAs(UnmanagedType.U4)]
            uint dwLanguageId,
            [param: MarshalAs(UnmanagedType.LPTStr)]
            out string lpBuffer,
            [param: MarshalAs(UnmanagedType.U4)]
            uint nSize,
            [param: MarshalAs(UnmanagedType.U4)]
            uint Arguments);

        public const uint FORMAT_MESSAGE_FROM_HMODULE = 0x800;

        public const uint FORMAT_MESSAGE_ALLOCATE_BUFFER = 0x100;
        public const uint FORMAT_MESSAGE_IGNORE_INSERTS = 0x200;
        public const uint FORMAT_MESSAGE_FROM_SYSTEM = 0x1000;
        public const uint FORMAT_MESSAGE_FLAGS = FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_FROM_SYSTEM;
    }
}