在没有打印对话框的情况下从 C# 中的 Windows 服务打印 html 文档

Question

我正在使用 Windows 服务，我想在服务启动时打印一个 .html 页面。我正在使用此代码，并且打印效果很好。但是打印对话框来了，没有打印对话框怎么打印？

public void printdoc(string document)
{
    Process printjob = new Process();
    printjob.StartInfo.FileName = document;
    printjob.StartInfo.UseShellExecute = true;
    printjob.StartInfo.Verb = "print";
    printjob.StartInfo.CreateNoWindow = true;
    printjob.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;

    printjob.Start();
}

有没有其他方法可以在不显示打印对话框的情况下打印它。

提前致谢， 阿努普帕尔

Answer 1

这是圣杯。

利用 StaTaskScheduler（取自 Parallel Extension Extras (release on Code Gallery)）。

特点：等待打印完成，不显示打印设置，希望可靠。

限制：需要 C# 4.0，使用默认打印机，不允许更改打印模板

    TaskScheduler Sta = new StaTaskScheduler(1);
    public void PrintHtml(string htmlPath)
    {
        Task.Factory.StartNew(() => PrintOnStaThread(htmlPath), CancellationToken.None, TaskCreationOptions.None, Sta).Wait();
    }

    void PrintOnStaThread(string htmlPath)
    {
        const short PRINT_WAITFORCOMPLETION = 2;
        const int OLECMDID_PRINT = 6;
        const int OLECMDEXECOPT_DONTPROMPTUSER = 2;
        using(var browser = new WebBrowser())
        {
            browser.Navigate(htmlPath);
            while(browser.ReadyState != WebBrowserReadyState.Complete)
                Application.DoEvents();

            dynamic ie = browser.ActiveXInstance;
            ie.ExecWB(OLECMDID_PRINT, OLECMDEXECOPT_DONTPROMPTUSER, PRINT_WAITFORCOMPLETION);
        }
    }

//--------------------------------------------------------------------------
// 
//  Copyright (c) Microsoft Corporation.  All rights reserved. 
// 
//  File: StaTaskScheduler.cs
//
//--------------------------------------------------------------------------

using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;

namespace System.Threading.Tasks.Schedulers
{
    /// <summary>Provides a scheduler that uses STA threads.</summary>
    public sealed class StaTaskScheduler : TaskScheduler, IDisposable
    {
        /// <summary>Stores the queued tasks to be executed by our pool of STA threads.</summary>
        private BlockingCollection<Task> _tasks;
        /// <summary>The STA threads used by the scheduler.</summary>
        private readonly List<Thread> _threads;

        /// <summary>Initializes a new instance of the StaTaskScheduler class with the specified concurrency level.</summary>
        /// <param name="numberOfThreads">The number of threads that should be created and used by this scheduler.</param>
        public StaTaskScheduler(int numberOfThreads)
        {
            // Validate arguments
            if (numberOfThreads < 1) throw new ArgumentOutOfRangeException("concurrencyLevel");

            // Initialize the tasks collection
            _tasks = new BlockingCollection<Task>();

            // Create the threads to be used by this scheduler
            _threads = Enumerable.Range(0, numberOfThreads).Select(i =>
            {
                var thread = new Thread(() =>
                {
                    // Continually get the next task and try to execute it.
                    // This will continue until the scheduler is disposed and no more tasks remain.
                    foreach (var t in _tasks.GetConsumingEnumerable())
                    {
                        TryExecuteTask(t);
                    }
                });
                thread.IsBackground = true;
                thread.SetApartmentState(ApartmentState.STA);
                return thread;
            }).ToList();

            // Start all of the threads
            _threads.ForEach(t => t.Start());
        }

        /// <summary>Queues a Task to be executed by this scheduler.</summary>
        /// <param name="task">The task to be executed.</param>
        protected override void QueueTask(Task task)
        {
            // Push it into the blocking collection of tasks
            _tasks.Add(task);
        }

        /// <summary>Provides a list of the scheduled tasks for the debugger to consume.</summary>
        /// <returns>An enumerable of all tasks currently scheduled.</returns>
        protected override IEnumerable<Task> GetScheduledTasks()
        {
            // Serialize the contents of the blocking collection of tasks for the debugger
            return _tasks.ToArray();
        }

        /// <summary>Determines whether a Task may be inlined.</summary>
        /// <param name="task">The task to be executed.</param>
        /// <param name="taskWasPreviouslyQueued">Whether the task was previously queued.</param>
        /// <returns>true if the task was successfully inlined; otherwise, false.</returns>
        protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
        {
            // Try to inline if the current thread is STA
            return
                Thread.CurrentThread.GetApartmentState() == ApartmentState.STA &&
                TryExecuteTask(task);
        }

        /// <summary>Gets the maximum concurrency level supported by this scheduler.</summary>
        public override int MaximumConcurrencyLevel
        {
            get { return _threads.Count; }
        }

        /// <summary>
        /// Cleans up the scheduler by indicating that no more tasks will be queued.
        /// This method blocks until all threads successfully shutdown.
        /// </summary>
        public void Dispose()
        {
            if (_tasks != null)
            {
                // Indicate that no new tasks will be coming in
                _tasks.CompleteAdding();

                // Wait for all threads to finish processing tasks
                foreach (var thread in _threads) thread.Join();

                // Cleanup
                _tasks.Dispose();
                _tasks = null;
            }
        }
    }
}

Answer 2

为了增加 Vadim 的限制，您可以在打印之前设置默认打印机，方法是：

    static void SetAsDefaultPrinter(string printerDevice)
    {
        foreach (var printer in PrinterSettings.InstalledPrinters)
        {
            //verify that the printer exists here
        }
        var path = "win32_printer.DeviceId='" + printerDevice + "'";
        using (var printer = new ManagementObject(path))
        {
            printer.InvokeMethod("SetDefaultPrinter",
                                 null, null);
        }

        return;
    }

并稍微改变 PrintHtml 方法：

    public void PrintHtml(string htmlPath, string printerDevice)
    {
        if (!string.IsNullOrEmpty(printerDevice))
            SetAsDefaultPrinter(printerDevice);


        Task.Factory.StartNew(() => PrintOnStaThread(htmlPath), CancellationToken.None, TaskCreationOptions.None, _sta).Wait();
    }

考虑到大量更改默认打印机可能会出现并发问题，我不知道这在繁重的打印环境中如何公平。但到目前为止，这是我想出的最好的解决此限制的方法。

Answer 3

在 Windows 服务中，Microsoft Web 浏览器控件不起作用。我使用过该代码，它在 Windows 应用程序中运行良好，但是当我在 Windows 服务中使用时，程序会卡在这一行

axWebBrowser1.Navigate(@"C:\mydoc.html", ref 空, ref 空, ref 空, ref 空);

感谢您的回复， 阿努普帕尔