在事件处理程序的主线程中执行方法 [英] Execute a method in main thread from event handler

问题描述

我有一个自Queue类继承的自定义Queue类.它有一个事件ItemAdded.在此事件的事件处理程序中，我正在执行一个方法.但是它正在运行而不是主线程，尽管我希望它在主线程中.我不知道该怎么做.有什么建议吗?

I have a custom Queue class inherited from Queue class. It has an event ItemAdded. In the event handler of this event i am executing a method. But it is running other than main thread, though i want it in main thread. I don't know how to do it. Any suggestion ?

//My custom class


using System;
using System.Collections; //Required to inherit non-generic Queue class.

namespace QueueWithEvent
{
    public class SmartQueue:Queue
    {

        public delegate void ItemAddedEventHandler(object sender, EventArgs e);

        public event ItemAddedEventHandler ItemAdded;

        protected virtual void OnItemAdded(EventArgs e)
        {
           if (ItemAdded != null)
           {
              ItemAdded(this, e);
           }
    }

    public override void Enqueue(object Item)
    {
        base.Enqueue(Item);
        OnItemAdded(EventArgs.Empty);
    }        

   }
}



 //Winform application

 using System;
 using System.ComponentModel;
 using System.Windows.Forms;
 using QueueWithEvent;

 namespace TestApp
 {
    public partial class Form1 : Form
    {

    SmartQueue qTest = new SmartQueue();

    public Form1()
    {
        InitializeComponent();
        qTest.ItemAdded += new SmartQueue.ItemAddedEventHandler(this.QChanged);
    }

    private void btnStartBgw_Click(object sender, EventArgs e)
    {
        DisplayThreadName();
        bgwTest.RunWorkerAsync();
    }

    private void bgwTest_DoWork(object sender, DoWorkEventArgs e)
    {
        try
        {
            for (int i = 0; i < 11; i++)
            {
                string valueTExt = i.ToString();
                qTest.Enqueue(valueTExt);
                System.Threading.Thread.Sleep(5000);
            }
        }
        catch (Exception Ex)
        {
            MessageBox.Show(Ex.Message);

        }
    }


    private void DisplayThreadName()
    {
        string tName = System.Threading.Thread.CurrentThread.ManagedThreadId.ToString();
        txtThreadName.Text = tName;           
    }

    private void QChanged(object sender, EventArgs e)
    {
        //#########I want this method to run on main thread #############
        DisplayThreadName();
    }
}
}

先谢谢了. 保罗.

推荐答案

您正在排队后台线程上的项目(DoWork事件处理程序在后台线程上运行)，因此您的事件也在后台线程中引发.

You are enqueueing items on background thread (DoWork event handler runs on background thread), thus your event raised also in background thread.

使用InvokeRequired方法来验证您是否在UI线程上.如果没有，请使用Invoke在UI线程上运行代码:

Use InvokeRequired method to verify if you are on UI thread. And if not, then use Invoke to run code on UI thread:

 private void QChanged(object sender, EventArgs e)
 {
     if (InvokeRequired)
     {
         Invoke((MethodInvoker)delegate { QChanged(sender, e); });
         return;
     }
     // this code will run on main (UI) thread 
     DisplayThreadName();
 }

另一个适合您的选项-使用ProgressChanged事件使项目入队(不要忘记将WorkerReportsProgress设置为true).此事件处理程序在UI线程上运行:

Another option for you - use ProgressChanged event to enqueue items (don't forget to set WorkerReportsProgress to true). This event handler runs on UI thread:

private void bgwTest_DoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker worker = (BackgroundWorker)sender;

    for (int i = 0; i < 11; i++)
    { 
        // use user state for passing data
        // which is not reflecting progress percentage
        worker.ReportProgress(0, i);
        System.Threading.Thread.Sleep(5000);
    }
}

private void bgwTest_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
     string valueTExt = e.UserState.ToString();
     qTest.Enqueue(valueTExt);
}

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