XInput.cs

using System.Runtime.InteropServices;

namespace Interop
{
    static class XInput
    {
        public const int XUserMaxCount = 4;

        /**
         * <summary>Sets the reporting state of XInput.</summary>
         * <param name="enable">
         * If enable is FALSE, XInput will only send neutral data in response to XInputGetState (all buttons up, axes centered, and triggers at 0).
         * XInputSetState calls will be registered but not sent to the device. Sending any value other than FALSE will restore reading and writing functionality to normal.
         * </param>
         */
        [DllImport("XInput1_4.dll")]
        public static extern void XInputEnable(
            [MarshalAs(UnmanagedType.Bool)]
            bool enable
        );

        /**
         * <summary>Retrieves the battery type and charge status of a wireless controller.</summary>
         * <param name="dwUserIndex">Index of the signed-in gamer associated with the device. Can be a value in the range 0–<see cref="XUserMaxCount"/> − 1.</param>
         * <param name="devType">Specifies which device associated with this user index should be queried. Must be <see cref="BatteryDevType.Gamepad"/> or <see cref="BatteryDevType.Headset"/>.</param>
         * <param name="pBatteryInformation">Pointer to an <see cref="XInputBatteryInformation"/> structure that receives the battery information.</param>
         * <returns>If the function succeeds, the return value is ERROR_SUCCESS.</returns>
         */
        [DllImport("XInput1_4.dll")]
        public static extern uint XInputGetBatteryInformation(
            int dwUserIndex,
            BatteryDevType devType,
            out XInputBatteryInformation pBatteryInformation
        );
    }

    /**
     * <summary>Contains information on battery type and charge state.</summary>
     */
    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    readonly struct XInputBatteryInformation
    {
        /**
         * <summary>The type of battery.</summary>
         */
        public readonly BatteryType BatteryType;
        /**
         * <summary>The charge state of the battery. This value is only valid for wireless devices with a known battery type.</summary>
         */
        public readonly BatteryLevel BatteryLevel;
    }

    enum BatteryDevType : byte
    {
        Gamepad = 0,
        Headset = 1,
    }

    enum BatteryType : byte
    {
        /**
         * <summary>The device is not connected.</summary>
         */
        Disconnected = 0x00,
        /**
         * <summary>The device is a wired device and does not have a battery.</summary>
         */
        Wired = 0x01,
        /**
         * <summary>The device has an alkaline battery.</summary>
         */
        Alkaline = 0x02,
        /**
         * <summary>The device has a nickel metal hydride battery.</summary>
         */
        NiMH = 0x03,
        /**
         * <summary>The device has an unknown battery type.</summary>
         */
        Unknown = 0xFF,
    }

    enum BatteryLevel : byte
    {
        Empty = 0x00,
        Low = 0x01,
        Medium = 0x02,
        Full = 0x03,
    }
}