显示模态窗口同时运行的BackgroundWorker，没有得到STA / MTA问题 [英] Showing Modal Window while BackgroundWorker runs, without getting STA/MTA issue

问题描述

我工作的一个WPF应用程序。我有一个耗时的，我想通过运行的BackgroundWorker 异步方法。虽然方法运行，我想显示一个模式请稍候...对话框窗口，它必须自动关闭时，的BackgroundWorker 完成。

我目前有的BackgroundWorker 很少经验或任何多线程编程。

下面当前的代码将导致一个出现InvalidOperationException ，与消息的调用线程必须STA ，因为许多UI组件都需要这一点。的

请告诉我。如果你能如何实现什么，我想实现的，额外的印象点帮助我了解什么错误。

非常感谢！

修改
只是为了澄清 - 这个想法是，主线程启动的BackgroundWorker ，然后显示模态对话框。当工人完成，它会关闭模态对话框。当模态对话框关闭，主线程继续。

 公共类ImageResizer 
 {
私人BackgroundWorker的工人; 
私人的MemoryStream的ImageData {搞定;组; } //传入数据
公私MemoryStream的ResizedImageData {搞定;私人集; } //得到的数据
私人Dialogs.WorkInProgressDialog ProgressDialog; 
 
 
 //公共接口，使用类调用：
公众的MemoryStream ReduceImageSize（MemoryStream的为imageData）
 {
 //注入​​数据：
 this.ImageData =为imageData; 
 
 //初始化进度对话框：
 ProgressDialog =新Dialogs.WorkInProgressDialog（）; 
 
 //启动后台工作的asyncronously没有工作
 =工作者新的BackgroundWorker（）; 
 worker.DoWork + =新DoWorkEventHandler（worker_DoWork）; 
 worker.RunWorkerCompleted + =新RunWorkerCompletedEventHandler（worker_RunWorkerCompleted）; 
 worker.RunWorkerAsync（）; 
 
 //显示进度对话框。对话框是模态，和调整时，必须只能望洋兴叹完成$ B（$ B ProgressDialog.ShowDialog）; //这行导致无效操作异常
 
 //此线程时ProgressDialog关闭只会继续。 
 
 //返回结果
返回ResizedImageData; 
} 
 
私人无效worker_DoWork（对象发件人，DoWorkEventArgs E）
 {
 //调用耗时的方法
 ResizedImageData = ReduceImageSize_ActualWork（）; 
} 
 
 //实际的工作方法，由一个名为worker_DoWork 
私人的MemoryStream ReduceImageSize_ActualWork（）
 {
 //很多的调整其大小的代码。的ImageData并将其分配给this.ResizedImageData 
} 
 
私人无效worker_RunWorkerCompleted（对象发件人，RunWorkerCompletedEventArgs E）
 {
 //异步工作完成 - 关闭进度对话框
 ProgressDialog.Close（）; 
} 
} 
  

解决方案

您不能从BackgroundWorker的调用ShowDialog的。你必须使用调度员问UI线程来执行它：

  this.Dispatcher.BeginInvoke（新动作（（） => ProgressDialog.ShowDialog（）））; 
  

在UI线程执行的BackgroundWorker的已完成的事件，所以这部分应该是罚款

I am working on a WPF application. I have a time consuming method that I want to run async via BackgroundWorker. While the method runs, I want to display a modal "Please Wait..." dialog window, which must automatically close when the BackgroundWorker completes.

I currently have very little experience with BackgroundWorker or any multi threaded programming.

The code below currently results in an InvalidOperationException, with the message "The calling thread must be STA, because many UI components require this."

Please advise me on how to achieve what I am trying to achieve, and extra brownie-points if you can help me understand what is going wrong.

Many thanks!

EDIT Just to clarify - The idea is that the main thread launches the BackgroundWorker, then shows the modal dialog. When the worker completes, it closes the modal dialog. When the modal dialog closes, the main thread continues.

public class ImageResizer
{
    private BackgroundWorker worker;
    private MemoryStream ImageData { get; set; } // incoming data
    private public MemoryStream ResizedImageData { get; private set; } // resulting data
    private Dialogs.WorkInProgressDialog ProgressDialog;


    // Public interface, called by using class:
    public MemoryStream ReduceImageSize(MemoryStream imageData)
    {
        // injected data:
        this.ImageData = imageData;

        // init progress dialog window:
        ProgressDialog = new Dialogs.WorkInProgressDialog();

        // Start background worker that asyncronously does work
        worker = new BackgroundWorker();
        worker.DoWork += new DoWorkEventHandler(worker_DoWork);
        worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);            
        worker.RunWorkerAsync();

        // Show progress dialog. Dialog is MODAL, and must only be closed when resizing is complete
        ProgressDialog.ShowDialog(); // THIS LINE CAUSES THE INVALID OPERATION EXCEPTION

        // This thread will only continue when ProgressDialog is closed.

        // Return result
        return ResizedImageData;
    }

    private void worker_DoWork(object sender, DoWorkEventArgs e)
    {
        // Call time consuming method
        ResizedImageData = ReduceImageSize_ActualWork();
    }

    // The actual work method, called by worker_DoWork
    private MemoryStream ReduceImageSize_ActualWork()
    {
        // Lots of code that resizes this.ImageData and assigns it to this.ResizedImageData
    }

    private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {   
        // Async work completed - close progress dialog
        ProgressDialog.Close();
    }
}

解决方案

You can't call ShowDialog from the BackgroundWorker. You have to use the Dispatcher to ask the UI thread to execute it:

 this.Dispatcher.BeginInvoke(new Action(() => ProgressDialog.ShowDialog()));

The 'Completed' event of the BackgroundWorker is executed in the UI thread, so this part should be fine.

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