C# – Prevent Windows workstation (desktop) from locking while running a WPF program

cnetwinapiwindows

Issue:
I have a WPF fullscreen application, which acts as a dashboard. The computer is in domain and domain policies enforce the computer to be locked in 10 minutes after the last user activity. I want to prevent the workstation (or desktop) from locking automatically.
An example of such behavior: Windows Media Player, which prevents this while a movie is running.

Known solutions (kinda workarounds):

It is possible to send a Win32 Mouse Move event every fixed interval of time (for example, every minute)
It is possible to send a key to the program (for example "Left Shift" key up) every fixed interval of time (for example, every minute)

QUESTION:
How can I prevent windows workstation from locking without using these workarounds?

Disclaimer:
I was pretty sure, there should be a similar question answered somewhere on StackOverflow, but i didn't find any. I would appreciate, if you could point me into the right direction.

Best Answer

The solution has been pointed out through the comments, but I'm providing a simple starter solution for anyone else arriving via a web search:

/// <summary>
/// Interaction logic for App.xaml
/// </summary>
public partial class App : Application
{
    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    static extern EXECUTION_STATE SetThreadExecutionState(EXECUTION_STATE esFlags);

    public App()
    {
        InitializeComponent();

        App.Current.Startup += new StartupEventHandler((sender, e) =>
            {
                SetThreadExecutionState(EXECUTION_STATE.ES_DISPLAY_REQUIRED | EXECUTION_STATE.ES_CONTINUOUS);
            });
        App.Current.Exit += new ExitEventHandler((sender, e) =>
            {
                SetThreadExecutionState(EXECUTION_STATE.ES_CONTINUOUS);
            });
    }
}

[FlagsAttribute]
public enum EXECUTION_STATE : uint
{
    ES_AWAYMODE_REQUIRED = 0x00000040,
    ES_CONTINUOUS = 0x80000000,
    ES_DISPLAY_REQUIRED = 0x00000002,
    ES_SYSTEM_REQUIRED = 0x00000001
    // Legacy flag, should not be used.
    // ES_USER_PRESENT = 0x00000004
}

An alternative place to put the logic would be within an event handler for StateChanged on your main application window:

this.StateChanged += new EventHandler((sender, e) =>
    {
        if (WindowState == System.Windows.WindowState.Maximized)
        {
            SetThreadExecutionState(EXECUTION_STATE.ES_DISPLAY_REQUIRED | EXECUTION_STATE.ES_CONTINUOUS);
        }
        else
        {
            SetThreadExecutionState(EXECUTION_STATE.ES_CONTINUOUS);
        }
    });

Related Solutions

Windows – Prevent windows from going into sleep when the program is running

After considering vim's answer

"Using PowerCreateRequest, PowerSetRequest, and PowerClearRequest functions is the preferred method."

with the linked AvailabilityRequests.docx on msdn which is exhausting to get into it (too much to read), I have searched the web for a concrete example in c# that is based on the PowerCreateRequest and found http://go4answers.webhost4life.com/Example/problem-monitor-wakeup-service-windows7-12092.aspx [EDIT 2016 - isn't available anymore]

Copied and adapted it to my needs (PInvoke of CloseHandle copied from msdn):

using System.Runtime.InteropServices;

    #region prevent screensaver, display dimming and automatically sleeping
    POWER_REQUEST_CONTEXT _PowerRequestContext;
    IntPtr _PowerRequest; //HANDLE

    // Availability Request Functions
    [DllImport("kernel32.dll")]
    static extern IntPtr PowerCreateRequest(ref POWER_REQUEST_CONTEXT Context);

    [DllImport("kernel32.dll")]
    static extern bool PowerSetRequest(IntPtr PowerRequestHandle, PowerRequestType RequestType);

    [DllImport("kernel32.dll")]
    static extern bool PowerClearRequest(IntPtr PowerRequestHandle, PowerRequestType RequestType);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
    internal static extern int CloseHandle(IntPtr hObject);

    // Availablity Request Enumerations and Constants
    enum PowerRequestType
    {
        PowerRequestDisplayRequired = 0,
        PowerRequestSystemRequired,
        PowerRequestAwayModeRequired,
        PowerRequestMaximum
    }

    const int POWER_REQUEST_CONTEXT_VERSION = 0;
    const int POWER_REQUEST_CONTEXT_SIMPLE_STRING = 0x1;
    const int POWER_REQUEST_CONTEXT_DETAILED_STRING = 0x2;

    // Availablity Request Structures
    // Note:  Windows defines the POWER_REQUEST_CONTEXT structure with an
    // internal union of SimpleReasonString and Detailed information.
    // To avoid runtime interop issues, this version of 
    // POWER_REQUEST_CONTEXT only supports SimpleReasonString.  
    // To use the detailed information,
    // define the PowerCreateRequest function with the first 
    // parameter of type POWER_REQUEST_CONTEXT_DETAILED.
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct POWER_REQUEST_CONTEXT
    {
        public UInt32 Version;
        public UInt32 Flags;
        [MarshalAs(UnmanagedType.LPWStr)]
        public string
            SimpleReasonString;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct PowerRequestContextDetailedInformation
    {
        public IntPtr LocalizedReasonModule;
        public UInt32 LocalizedReasonId;
        public UInt32 ReasonStringCount;
        [MarshalAs(UnmanagedType.LPWStr)]
        public string[] ReasonStrings;
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct POWER_REQUEST_CONTEXT_DETAILED
    {
        public UInt32 Version;
        public UInt32 Flags;
        public PowerRequestContextDetailedInformation DetailedInformation;
    }
    #endregion



    /// <summary>
    /// Prevent screensaver, display dimming and power saving. This function wraps PInvokes on Win32 API. 
    /// </summary>
    /// <param name="enableConstantDisplayAndPower">True to get a constant display and power - False to clear the settings</param>
    private void EnableConstantDisplayAndPower(bool enableConstantDisplayAndPower)
    {
        if (enableConstantDisplayAndPower)
        {
            // Set up the diagnostic string
            _PowerRequestContext.Version = POWER_REQUEST_CONTEXT_VERSION;
            _PowerRequestContext.Flags = POWER_REQUEST_CONTEXT_SIMPLE_STRING;
            _PowerRequestContext.SimpleReasonString = "Continuous measurement"; // your reason for changing the power settings;

            // Create the request, get a handle
            _PowerRequest = PowerCreateRequest(ref _PowerRequestContext);

            // Set the request
            PowerSetRequest(_PowerRequest, PowerRequestType.PowerRequestSystemRequired);
            PowerSetRequest(_PowerRequest, PowerRequestType.PowerRequestDisplayRequired);
        }
        else
        {
            // Clear the request
            PowerClearRequest(_PowerRequest, PowerRequestType.PowerRequestSystemRequired);
            PowerClearRequest(_PowerRequest, PowerRequestType.PowerRequestDisplayRequired);

            CloseHandle(_PowerRequest);
        }
    }

C# – Transitioning from Windows Forms to WPF

I like to blog about beginner articles for WPF, and there are a few in particular that may help you out:

To summarize, the biggest difference between Winforms and WPF is that in WPF your data layer (the DataContext) is your application, while in Winforms your UI layer is your application.

To look at it another way, with WPF your application consists of the objects you create, and you use Templates and other UI objects to tell WPF how to draw your application components.

That's the opposite of WinForms where you build your application out of UI objects, and then supply them with the data needed.

Because of this, the designer isn't actually used that much since your application components are designed in code, and the designer is only needed to draw a user-friendly interface that reflects your data classes (typically Models and ViewModels)

And personally, I prefer to type all my XAML out by hand since it's faster and doesn't make as much of a mess as the drag/drop WPF designer does, although I do use the Designer on occasion to preview what my UI will look like.

So to your answer your question about if there's other WPF designers suited for WinForms developers, I would suggest that instead of looking for another designer, instead look to learn how to use WPF in the way it's meant to be used. Using WPF like it's WinForms means you miss out on much of what makes it so great :)

Best Answer

Related Solutions

Windows – Prevent windows from going into sleep when the program is running

C# – Transitioning from Windows Forms to WPF

Related Topic