C# .NET: How to check if we're running on battery?

I believe you can check SystemInformation.PowerStatus to see if it's on battery or not.

Boolean isRunningOnBattery =
      (System.Windows.Forms.SystemInformation.PowerStatus.PowerLineStatus == 
       PowerLineStatus.Offline);

Edit: In addition to the above, there's also a System.Windows.Forms.PowerStatus class. One of its methods is PowerLineStatus, which will equal PowerLineStatus.Online if it's on AC Power.

R. Bemrose found the managed call. Here's some sample code:

/// <summary>
/// Indicates if we're running on battery power.
/// If we are, then disable CPU wasting things like animations, background operations, network, I/O, etc
/// </summary>
public static Boolean IsRunningOnBattery
{
   get
   {
      PowerLineStatus pls = System.Windows.Forms.SystemInformation.PowerStatus.PowerLineStatus;

      //Offline means running on battery
      return (pls == PowerLineStatus.Offline);
   }
}

You could use the GetSystemPowerStatus function using P/Invoke. See: http://msdn.microsoft.com/en-gb/library/aa372693.aspx

Here's an example:

using System;
using System.Runtime.InteropServices;
namespace PowerStateExample
{
    [StructLayout(LayoutKind.Sequential)]
    public class PowerState
    {
        public ACLineStatus ACLineStatus;
        public BatteryFlag BatteryFlag;
        public Byte BatteryLifePercent;
        public Byte Reserved1;
        public Int32 BatteryLifeTime;
        public Int32 BatteryFullLifeTime;

        // direct instantation not intended, use GetPowerState.
        private PowerState() {}

        public static PowerState GetPowerState()
        {
            PowerState state = new PowerState();
            if (GetSystemPowerStatusRef(state))
                return state;

            throw new ApplicationException("Unable to get power state");
        }

        [DllImport("Kernel32", EntryPoint = "GetSystemPowerStatus")]
        private static extern bool GetSystemPowerStatusRef(PowerState sps);
    }

    // Note: Underlying type of byte to match Win32 header
    public enum ACLineStatus : byte
    {
        Offline = 0, Online = 1, Unknown = 255
    }

    public enum BatteryFlag : byte
    {
        High = 1, Low = 2, Critical = 4, Charging = 8,
        NoSystemBattery = 128, Unknown = 255
    }

    // Program class with main entry point to display an example.
    class Program
    {        
        static void Main(string[] args)
        {
            PowerState state = PowerState.GetPowerState();
            Console.WriteLine("AC Line: {0}", state.ACLineStatus);
            Console.WriteLine("Battery: {0}", state.BatteryFlag);
            Console.WriteLine("Battery life %: {0}", state.BatteryLifePercent);
        }
    }
}