Reactive Extension(Rx)使用

(這不是BCB的RX)

MSDN Reactive Extension 介紹

Reactive Extensions概要

Reactive Extension入門

textBox的文字在TextChanged事件發生時同步

var res = from evt in Observable.FromEventPattern(textBox1, "TextChanged")
          select ((TextBox) evt.Sender).Text;
res.Subscribe(text => textBox2.Text = text);

在Winform表單上繪圖

將滑鼠事件轉成Observable集合後，籍由Subscribe訂閱事件發生時想要的操作，完成一般要分散在三個滑鼠事件中撰寫的工作。

private Point _startPoint;

private void Form1_Load(object sender, EventArgs e)
{
    WireUpEvents();
}

private void WireUpEvents()
{
    var mouseDown = Observable.FromEventPattern<MouseEventArgs>(this, "MouseDown")
        .Select(arg => arg.EventArgs.Location);

    var mouseMove = Observable.FromEventPattern<MouseEventArgs>(this, "MouseMove")
        .Select(arg => arg.EventArgs.Location);

    var mouseUp = Observable.FromEventPattern<MouseEventArgs>(this, "MouseUp")
        .Select(arg => arg.EventArgs.Location);

    var mouseDrag = mouseMove
        .SkipUntil(mouseDown)
        .TakeUntil(mouseUp)
        .Repeat();

    // remember the point when mouse down
    mouseDown.Subscribe(pos => _startPoint = pos);

    // show dragging position
    mouseDrag.Subscribe(pos => label1.Text = pos.ToString());
    mouseDrag.Subscribe(currentPos =>
    {
        using (var g = this.CreateGraphics())
        {
            if (_startPoint == currentPos)
                return;

            g.DrawLine(new Pen(Color.Green), _startPoint, currentPos);
            _startPoint = currentPos;
        }
    });
}

另有UI整合的Framework，也是很有趣的一個應用
ReactiveUI(MVVM with Rx)