mirror of https://github.com/dahall/Vanara.git
75 lines
3.6 KiB
C#
75 lines
3.6 KiB
C#
using System;
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using System.Runtime.InteropServices;
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using System.Windows.Forms;
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using Vanara.PInvoke;
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using static Vanara.PInvoke.User32;
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namespace Vanara.Windows.Forms.Forms
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{
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/// <summary>Used to define a set of operations within which any shutdown request will be met with a reason why this application is blocking it.</summary>
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/// <remarks>This is to be used in either a 'using' statement or for the life of the application.
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/// <para>To use for the life of the form, define a class field:
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/// <code lang="cs">
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/// private PreventShutdownContext disallowShutdown;
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///
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/// protected override void OnHandleCreated(EventArgs e)
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/// {
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/// base.OnHandleCreated(e);
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/// disallowShutdown = new PreventShutdownContext(this, "Application defined message goes here.");
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/// }
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/// </code></para>
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/// <para>To use this for a section of code:
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/// <code lang="cs">
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/// using (new PreventShutdownContext(this, "This app is super busy right now."))
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/// {
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/// // Do something that can't be interrupted...
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/// }
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/// </code></para></remarks>
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public class PreventShutdownContext : IDisposable
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{
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private const int WM_QUERYENDSESSION = 0x11;
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private HandleRef href;
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/// <summary>Initializes a new instance of the <see cref="PreventShutdownContext" /> class.</summary>
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/// <param name="window">The <see cref="Form" /> that contains a valid window handle.</param>
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/// <param name="reason">The reason the application must block system shutdown. Because users are typically in a hurry when shutting down the system, they may spend only a few seconds looking at the shutdown reasons that are displayed by the system. Therefore, it is important that your reason strings are short and clear.</param>
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/// <param name="tryToPreventShutdown">If set to <see langword="true" />, this class will return false to the WM_QUERYENDSESSION by handling the e.Cancel response to Form.FormClosing.</param>
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/// <exception cref="SystemException">The system is configured to bypass showing application reasons for preventing shutdown.</exception>
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public PreventShutdownContext(Form window, string reason, bool tryToPreventShutdown = false)
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{
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if ((Microsoft.Win32.Registry.GetValue(@"HKEY_USERS\.DEFAULT\Control Panel\Desktop", "AutoEndTasks", 0) is uint v1 && v1 == 1) ||
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(Microsoft.Win32.Registry.GetValue(@"HKEY_CURRENT_USER\Control Panel\Desktop", "AutoEndTasks", 0) is uint v2 && v2 == 1))
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throw new SystemException("The system is configured to bypass showing application reasons for preventing shutdown.");
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href = new HandleRef(window, window.Handle);
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if (tryToPreventShutdown)
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window.FormClosing += (s, e) => e.Cancel = true;
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Reason = reason;
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}
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/// <summary>The reason the application must block system shutdown. Because users are typically in a hurry when shutting down the system, they may spend only a few seconds looking at the shutdown reasons that are displayed by the system. Therefore, it is important that your reason strings are short and clear.</summary>
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/// <value>The reason string.</value>
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public string Reason
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{
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get
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{
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if (!ShutdownBlockReasonQuery(href.Handle, out var reason))
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Win32Error.ThrowLastError();
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return reason;
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}
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set
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{
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if (value == null) value = string.Empty;
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if (ShutdownBlockReasonQuery(href.Handle, out var _))
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ShutdownBlockReasonDestroy(href.Handle);
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if (!ShutdownBlockReasonCreate(href.Handle, value))
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Win32Error.ThrowLastError();
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}
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}
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/// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
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public void Dispose()
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{
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ShutdownBlockReasonDestroy(href.Handle);
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}
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}
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} |