C#调用windows api获得当前活动的窗体的标题？

Question

1、是SetCapture，以便鼠标在窗口外的点击也能发送到本窗口，
2、是用WindowFromPoint找到目标窗口，
3、也就是GetWindowText了。
简单例子如下：    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.button1.Text = "Start Capture";
        }        private void button1_Click(object sender, EventArgs e)
        {
            this.button1.Text = "Capturing...";
            this.Text = "Now click on the target window";
            this.Capture = true;
        }        protected override void OnMouseDown(MouseEventArgs e)
        {
            base.OnMouseDown(e);
            this.button1.Text = "Start Capture";            if (this.Capture)
            {
                IntPtr target = WindowFromPoint(this.PointToScreen(e.Location));
                if (target != IntPtr.Zero)
                {
                    StringBuilder sb = new StringBuilder(256);
                    GetWindowTextW(target, sb, 256);
                    this.Text = sb.ToString();
                }
            }
        }
        [DllImport("User32")]
        static extern IntPtr WindowFromPoint(Point point);        [DllImport("User32", CharSet = CharSet.Unicode)]
        static extern int GetWindowTextW(IntPtr hWnd, StringBuilder sb, int maxCount);
    }