问题描述
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在我的多线程应用程序中，我需要对UI元素进行跨线程访问，并且我正在使用线程安全的方法来做到这一点。我在我的许多项目中反复使用了很多，并将它们保留在表单文件本身中会使文件看起来很丑。所以我想创建一个单独的类，在其中我可以放所有这些，并在需要时调用它们，但我遇到了麻烦。为了实例化更改控件的文本元素，我正在使用以下代码
delegate void SetTextCallback(string text,Control ctrl);
public void SetText(string text,Control ctrl)
{
if (ctrl.Invokerequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d,new object[] { text,ctrl });
}
else
{
if (ctrl.GetType() == typeof(Label))
{
ctrl.Text = text;
}
else
{
ctrl.Text += Environment.NewLine + text;
}
}
}
SetText(\"some text\",label1);
this.Invoke(d,ctrl });
public void ChangePropert(Control ctrl,Property prop,Value val)
解决方法
所有这些的问题是您开始泄漏控件实际所在的窗体之外的UI代码。线程不必知道控件，它应该工作并更新主线程，并让主线程担心需要在UI中完成什么。
完成此操作的方法是具有第二个线程可以调用的回调，但是强制该回调实际上在主线程上执行，而不是在第二个线程上执行。您可以通过使用同步上下文来完成此操作。
您需要将辅助线程包装在一个类中，该类可以保留对主线程同步上下文的引用。然后，辅助线程可以将其用于回调。
例：
public partial class Form1 : Form
{
private SynchronizationContext _synchronizationContext;
public Form1()
{
InitializeComponent();
//Client must be careful to create sync context somehwere they are sure to be on main thread
_synchronizationContext = AsyncOperationManager.SynchronizationContext;
}
//Callback method implementation - must be of this form
public void ReceiveThreadData(object threadData)
{
// This callback now exeutes on the main thread.
// Can use directly in UI without error
this.listBoxMain.Items.Add((string)threadData);
}
private void DoSomeThreadWork()
{
// Thread needs callback and sync context so it must be wrapped in a class.
SendOrPostCallback callback = new SendOrPostCallback(ReceiveThreadData);
SomeThreadTask task = new SomeThreadTask(_synchronizationContext,callback);
Thread thread = new Thread(task.ExecuteThreadTask);
thread.Start();
}
private void button1_Click(object sender,EventArgs e)
{
DoSomeThreadWork();
}
}
/// SomeThreadTask defines the work a thread needs to do and also provides any data ///required along with callback pointers etc.
/// Populate a new SomeThreadTask instance with a synch context and callnbackl along with ///any data the thread needs
/// then start the thread to execute the task.
/// </summary>
public class SomeThreadTask
{
private string _taskId;
private SendOrPostCallback _completedCallback;
private SynchronizationContext _synchronizationContext;
/// <summary>
/// Get instance of a delegate used to notify the main thread when done.
/// </summary>
internal SendOrPostCallback CompletedCallback
{
get { return _completedCallback; }
}
/// <summary>
/// Get SynchronizationContext for main thread.
/// </summary>
internal SynchronizationContext SynchronizationContext
{
get { return _synchronizationContext; }
}
/// <summary>
/// Thread entry point function.
/// </summary>
public void ExecuteThreadTask()
{
//Just sleep instead of doing any real work
Thread.Sleep(5000);
string message = \"This is some spoof data from thread work.\";
// Execute callback on synch context to tell main thread this task is done.
SynchronizationContext.Post(CompletedCallback,(object)message);
}
public SomeThreadTask(SynchronizationContext synchronizationContext,SendOrPostCallback callback)
{
_synchronizationContext = synchronizationContext;
_completedCallback = callback;
}
}
label1.SetText(\"some text\");
SetText(\"some text\",label1);
var textProperty = label1.GetType().GetProperty(\"Text\");
textProperty.SetValue(label1,\"some text\",null);