MonitorHelper

public class MonitorHelper {

    #region consts
        const UInt32 SDC_TOPOLOGY_INTERNAL = 0x00000001;
        const UInt32 SDC_TOPOLOGY_CLONE = 0x00000002;
        const UInt32 SDC_TOPOLOGY_EXTEND = 0x00000004;
        const UInt32 SDC_TOPOLOGY_EXTERNAL = 0x00000008;

        const UInt32 SDC_USE_SUPPLIED_DISPLAY_CONFIG = 0x00000020;
        const UInt32 SDC_VALIDATE = 0x00000040;
        const UInt32 SDC_APPLY = 0x00000080;
        const UInt32 SDC_NO_OPTIMIZATION = 0x00000100;
        const UInt32 SDC_SAVE_TO_DATABASE = 0x00000200;
        const UInt32 SDC_ALLOW_CHANGES = 0x00000400;
        const UInt32 SDC_PATH_PERSIST_IF_REQUIRED = 0x00000800;
        const UInt32 SDC_FORCE_MODE_ENUMERATION = 0x00001000;
        const UInt32 SDC_ALLOW_PATH_ORDER_CHANGES = 0x00002000;

        const UInt32 QDC_ALL_PATHS = 0x00000001;
        const UInt32 QDC_ONLY_ACTIVE_PATHS = 0x00000002;
        const UInt32 QDC_DATABASE_CURRENT = 0x00000004;
    #endregion

    [Serializable]
    public class TVSettings {
        public DISPLAYCONFIG_PATH_INFO[] Path;
        public DISPLAYCONFIG_MODE_INFO[] Mode;
    }

    public static TVSettings Enabled;
    public static TVSettings Disabled;

    [DllImport("User32.dll")]
    public static extern int GetDisplayConfigBufferSizes(uint flags, ref uint numPathArrayElements, ref uint numModeInfoArrayElements);
    [DllImport("User32.dll")]
    public static extern int QueryDisplayConfig(
        uint flags,
        ref uint numPathArray, [Out] DISPLAYCONFIG_PATH_INFO[] pathArray,
        ref uint numModeArray, [Out] DISPLAYCONFIG_MODE_INFO[] modeArray,
        IntPtr currentTopologyId
    );
    [DllImport("User32.dll")]
    public static extern int SetDisplayConfig(
        uint numPathArray,  [In] DISPLAYCONFIG_PATH_INFO[] pathArray,
        uint numModeArray,  [In] DISPLAYCONFIG_MODE_INFO[] modeArray,
        uint flags
    );

    public static void ChangeTVState(bool Update = false, bool Save = false) {
        uint numPathArrayElements = 0;
        uint numModeInfoArrayElements = 0;
        uint id = QDC_ALL_PATHS;

        int bufferError = GetDisplayConfigBufferSizes(id, ref numPathArrayElements, ref numModeInfoArrayElements);
        DISPLAYCONFIG_PATH_INFO[] pathArray = new DISPLAYCONFIG_PATH_INFO[numPathArrayElements];
        DISPLAYCONFIG_MODE_INFO[] modeArray = new DISPLAYCONFIG_MODE_INFO[numModeInfoArrayElements];

        QueryDisplayConfig(id, ref numPathArrayElements, pathArray, ref numModeInfoArrayElements, modeArray, IntPtr.Zero);

        var active_modeArray = modeArray.Where(x => x.targetMode.targetVideoSignalInfo.activeSize.cx != 0).ToArray();
        var active_pathArray = pathArray.Where(x => x.flags != 0).ToArray();

        bool ThirdScreenIsConnected = active_pathArray.Length >= 3 && active_modeArray.Length >= 3;

        if (Save) {
            if (ThirdScreenIsConnected) {
                Disabled = new TVSettings() {
                    Path = pathArray,
                    Mode = modeArray
                };
            }
            else {
                Enabled = new TVSettings() {
                    Path = pathArray,
                    Mode = modeArray
                };
            }
        }

        if (Update) {
            if (Enabled == null || Disabled == null) {
                Console.WriteLine("Enabled & Disabled Settings are not configured properly.");
                Console.WriteLine("Please save both and try again.");
                return;
            }

            var Settings = ThirdScreenIsConnected ? Enabled : Disabled;
            pathArray = Settings.Path;
            modeArray = Settings.Mode;

            int f = SetDisplayConfig((uint)pathArray.Length, pathArray, (uint)modeArray.Length, modeArray, (SDC_APPLY | SDC_SAVE_TO_DATABASE | SDC_ALLOW_CHANGES | SDC_USE_SUPPLIED_DISPLAY_CONFIG));

            if (f == 0) { Console.WriteLine("Successfully updated Screen setup!"); }
            else { Console.WriteLine("SetDisplayConfig ERROR: " + f); }
        }

    }

}