Marc Gravell的.NET 4最简单解决方案的变体：

control.Invoke((MethodInvoker) (() => control.Text = "new text"));

或者改用Action委托：

control.Invoke(new Action(() => control.Text = "new text"));

请参阅此处了解两者的比较：MethodInvoker与Action for Control.BeginInvoke

线程代码经常有bug，而且总是很难测试。您不需要编写线程代码来从后台任务更新用户界面。只需使用BackgroundWorker类来运行任务及其ReportProgress方法来更新用户界面。通常，您只报告完成百分比，但还有一个重载包含状态对象。下面是一个仅报告字符串对象的示例：

    private void button1_Click(object sender, EventArgs e)
    {
        backgroundWorker1.WorkerReportsProgress = true;
        backgroundWorker1.RunWorkerAsync();
    }

    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        Thread.Sleep(5000);
        backgroundWorker1.ReportProgress(0, "A");
        Thread.Sleep(5000);
        backgroundWorker1.ReportProgress(0, "B");
        Thread.Sleep(5000);
        backgroundWorker1.ReportProgress(0, "C");
    }

    private void backgroundWorker1_ProgressChanged(
        object sender, 
        ProgressChangedEventArgs e)
    {
        label1.Text = e.UserState.ToString();
    }

如果您总是想更新同一个字段，这很好。如果要进行更复杂的更新，可以定义一个类来表示UI状态，并将其传递给ReportProgress方法。

最后一件事，确保设置WorkerReportsProgress标志，否则ReportProgress方法将被完全忽略。

例如，访问当前线程以外的控件：

Speed_Threshold = 30;
textOutput.Invoke(new EventHandler(delegate
{
    lblThreshold.Text = Speed_Threshold.ToString();
}));

lblThreshold是一个标签，Speed_Threshold则是一个全局变量。

关于这个主题的另一个示例：我创建了一个抽象类UiSynchronizeModel，它包含一个公共方法实现：

public abstract class UiSynchronizeModel
{
    private readonly TaskScheduler uiSyncContext;
    private readonly SynchronizationContext winformsOrDefaultContext;

    protected UiSynchronizeModel()
    {
        this.winformsOrDefaultContext = SynchronizationContext.Current ?? new SynchronizationContext();
        this.uiSyncContext = TaskScheduler.FromCurrentSynchronizationContext();
    }

    protected void RunOnGuiThread(Action action)
    {
        this.winformsOrDefaultContext.Post(o => action(), null);
    }

    protected void CompleteTask(Task task, TaskContinuationOptions options, Action<Task> action)
    {
        task.ContinueWith(delegate
        {
            action(task);
            task.Dispose();
        }, CancellationToken.None, options, this.uiSyncContext);
    }
}

模型或控制器类应从此抽象类派生。您可以使用任何模式（任务或手动管理的后台线程）并使用以下方法：

public void MethodThatCalledFromBackroundThread()
{
   this.RunOnGuiThread(() => {
       // Do something over UI controls
   });
}

任务示例：

var task = Task.Factory.StartNew(delegate
{
    // Background code
    this.RunOnGuiThread(() => {
        // Do something over UI controls
    });
});

this.CompleteTask(task, TaskContinuationOptions.OnlyOnRanToCompletion, delegate
{
    // Code that can safely use UI controls
});

基本上，无论框架版本或GUI底层库类型如何，解决此问题的方法都是保存控件，为工作线程创建线程的同步上下文，从而将控件的相关交互从工作线程编组到GUI的线程消息队列。

例子：

SynchronizationContext ctx = SynchronizationContext.Current; // From control
ctx.Send\Post... // From worker thread

也许有点过量，但这是我通常解决问题的方式：

由于同步，此处不需要调用。BasicClassThreadExample对我来说只是一种布局，因此请根据您的实际需要进行更改。

这很简单，因为您不需要处理UI线程中的内容！

public partial class Form1 : Form
{
    BasicClassThreadExample _example;

    public Form1()
    {
        InitializeComponent();
        _example = new BasicClassThreadExample();
        _example.MessageReceivedEvent += _example_MessageReceivedEvent;
    }

    void _example_MessageReceivedEvent(string command)
    {
        listBox1.Items.Add(command);
    }

    private void button1_Click(object sender, EventArgs e)
    {
        listBox1.Items.Clear();
        _example.Start();
    }
}

public class BasicClassThreadExample : IDisposable
{
    public delegate void MessageReceivedHandler(string msg);

    public event MessageReceivedHandler MessageReceivedEvent;

    protected virtual void OnMessageReceivedEvent(string msg)
    {
        MessageReceivedHandler handler = MessageReceivedEvent;
        if (handler != null)
        {
            handler(msg);
        }
    }

    private System.Threading.SynchronizationContext _SynchronizationContext;
    private System.Threading.Thread _doWorkThread;
    private bool disposed = false;

    public BasicClassThreadExample()
    {
        _SynchronizationContext = System.ComponentModel.AsyncOperationManager.SynchronizationContext;
    }

    public void Start()
    {
        _doWorkThread = _doWorkThread ?? new System.Threading.Thread(dowork);

        if (!(_doWorkThread.IsAlive))
        {
            _doWorkThread = new System.Threading.Thread(dowork);
            _doWorkThread.IsBackground = true;
            _doWorkThread.Start();
        }
    }

    public void dowork()
    {
        string[] retval = System.IO.Directory.GetFiles(@"C:\Windows\System32", "*.*", System.IO.SearchOption.TopDirectoryOnly);
        foreach (var item in retval)
        {
            System.Threading.Thread.Sleep(25);
            _SynchronizationContext.Post(new System.Threading.SendOrPostCallback(delegate(object obj)
            {
                OnMessageReceivedEvent(item);
            }), null);
        }
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!disposed)
        {
            if (disposing)
            {
                _doWorkThread.Abort();
            }
            disposed = true;
        }
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    ~BasicClassThreadExample() { Dispose(false); }

}