无效的跨线程访问。错误

Question

我在silverlight有一个网页表格。

单击某个按钮的操作时，我想更新另一个控件，如图表、文本框等。

同时，当它填充图表或文本框时，我需要显示一个繁忙的指示器。

1. 繁忙指示器应首先显示在屏幕上，
2. 后面的图表值应得到更新，
3. 图值将反映在屏幕上
4. 繁忙指示器应隐藏

但问题是，当我尝试使用线程时，我得到了一个错误“无效的跨线程访问”。当线程正在访问UI控件时。我尝试过的四个步骤如下。

任何有价值的建议如何解决这个问题。

步骤1 =>尝试了线程

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Threading;
using System.ComponentModel;
using System.Windows.Threading;


namespace SilverlightApplication2
{
  public partial class MainPage : UserControl
    {

        public MainPage()
        {
            InitializeComponent();



        }

        private void test1()
        {


            for (int i = 1; i < 10000; i++)
            {
                System.Diagnostics.Debug.WriteLine(i.ToString());
            }
        textbox1.Text="test";   //=> Throwing Error "Invalid cross-thread access."
            busyIndicator1.IsBusy = false;   //=> Throwing Error "Invalid cross-thread access."
        }



     private void button1_Click(object sender, RoutedEventArgs e)
         {
             busyIndicator1.IsBusy = true;

             Thread th1 = new Thread(test1);
             th1.Start();

         }

    }
}

步骤2 =>尝试了BackgroundWorker

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Threading;
using System.ComponentModel;
using System.Windows.Threading;


namespace SilverlightApplication2
{
  public partial class MainPage : UserControl
    {

        public MainPage()
        {
            InitializeComponent();



        }

        private void test1()
        {


            for (int i = 1; i < 10000; i++)
            {
                System.Diagnostics.Debug.WriteLine(i.ToString());
            }
        textbox1.Text="test";   //=> Throwing Error "Invalid cross-thread access."
            busyIndicator1.IsBusy = false;   //=> Throwing Error "Invalid cross-thread access."
        }



     private void button1_Click(object sender, RoutedEventArgs e)
         {
             busyIndicator1.IsBusy = true;

            var bw = new BackgroundWorker();
            bw.DoWork += (s, args) =>
            {
                test1();  //Stuff that takes some time
            };
            bw.RunWorkerCompleted += (s, args) =>
            {
                busyIndicator1.IsBusy = false;
            };
            bw.RunWorkerAsync();              
         }

    }
}

步骤3 =>试图从后面的代码引发一个事件

public delegate void LinkToEventHandler();
public static event LinkToEventHandler Evt;

 private void button1_Click(object sender, RoutedEventArgs e)
 {
     busyIndicator1.IsBusy = true;

     Evt += new LinkToEventHandler(this.test1);
     Evt();
 }



private void test1()
{


    for (int i = 1; i < 10000; i++)
    {
        System.Diagnostics.Debug.WriteLine(i.ToString());
    }
    textbox1.Text="test";   //=> Throwing Error "Invalid cross-thread access."
    busyIndicator1.IsBusy = false;   //=> Throwing Error "Invalid cross-thread access."
}

步骤4 =>尝试绑定Busy指示器

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Threading;
using System.ComponentModel;
using System.Windows.Threading;


namespace SilverlightApplication2
{
    public partial class MainPage : INotifyPropertyChanged
    {
        public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;
        public const string IsBusyPropertyName = "busyIndicator1";
        private bool _isBusy = false;
        public bool IsBusy
        {
            get
            {
                return _isBusy;
            }
            set
            {
                if (_isBusy != value)
                {
                    _isBusy = value;
                    RaisePropertyChanged(IsBusyPropertyName);
                }
            }
        }

        protected void RaisePropertyChanged(string propertyName)
        {
            System.ComponentModel.PropertyChangedEventHandler propertyChanged = this.PropertyChanged;
            if ((propertyChanged != null))
            {
                propertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
            }
        }


        private void button1_Click(object sender, RoutedEventArgs e)
        {

            IsBusy = true;

            test1();

            IsBusy=false;

        }

    }


    public partial class MainPage : UserControl
    {

        public MainPage()
        {
            InitializeComponent();



        }


        private void test1()
        {


            for (int i = 1; i < 10000; i++)
            {
                System.Diagnostics.Debug.WriteLine(i.ToString());
            }


        }



    }
}

注意：-我想要一个解决方案，它应该在silverlight中的Web表单中工作，而不是在windows窗体中。

Answer 1

这应该对你有用。本质上，将处理代码放在线程中，然后通过Dispatcher返回您的UI控件。

 public partial class MainPage : UserControl
    {
        private Thread _thread1;

        public MainPage()
        {
            InitializeComponent();
        }

        private void StartThreads()
        {
            _thread1 = new Thread(test1);
            _thread1.Start();
        }
        private void button1_Click(object sender, RoutedEventArgs e)
        {
            busyIndicator1.IsBusy = true;
            StartThreads();
        }

        private void test1()
        {
            for (int i = 1; i < 10000; i++)
            {
                System.Diagnostics.Debug.WriteLine(i.ToString());
            }
            this.Dispatcher.BeginInvoke(delegate()
            {
                textBox1.Text = "test";
                busyIndicator1.IsBusy = false;
            });
        }
    }

Answer 2

之所以会出现此错误，是因为UI方法只能在UI (也称为Dispatcher)线程上调用。要克服在另一个线程上执行UI操作的要求，您应该调用主UI线程上的操作。(见下文)

内联调用

// Disable some control
this.Dispatcher.BeginInvoke(new Action(() => this.SomeControl.IsEnabled = false));

方法驱动的调用

private void SomeMethodRunningOnAnotherThread()
{
    // ... perform some operations

    // Update the UI
    UpdateUI();

    // ... perform more operations
}

private void UpdateUI()
{
    // Make sure we're running on the UI thread
    if (!CheckAccess())
    {
        this.Dispatcher.BeginInvoke(new Action(UpdateUI));
        return;
    }

    // Disable some control
    this.SomeControl.IsEnabled = false;
}

在大多数情况下，第二种方法可能更好--特别是在执行多个UI操作时。值得注意的是，一旦UI线程处于空闲状态，这些UI操作将在UI线程上执行，因此，如果您已经在执行其他操作，您将不会看到更新。此外，通过使用BeginInvoke，您不会阻塞调用线程。