如何绘制根据鼠标的移动的矩形？

我找到的样本代码在这里窗体上图：

I found sample code here for drawing on a form:

的 http://msdn.microsoft.com/en-us/library/aa287522（v = vs.71）的.aspx

作为后续这一要求（发现哪些控件是$ b $拖动鼠标所记载的b用户的矩形下）：

As a followup to this requirement (discovering which controls are beneath a rectangle described by the user dragging the mouse):

的似乎是我的控件的位置和我的MouseDown的位置和-Up事件之间的不匹配

...我想提供用户即时/关于他们即将选择
正是不断的反馈（当/如果他们松开鼠标按钮）。我想不只是画下鼠标的
运动的路线，但是画正由他们mousewrangling努力所描述的矩形。

...I want to provide the user instant/constant feedback about just what they are about to select (when/if they release the mouse button). I want to not just draw a line following the mouse's movement, but draw the rectangle that is being described by their mousewrangling efforts.

我想的MouseMove事件，上面再加码从两个环节，可以做的伎俩，但是，这是被炒得经常/它会带来性能上的一个恶毒的影响？如果是这样，这将是挂钩较好的情况下，或将定时器是去这里的方式？

I'm thinking the MouseMove event, coupled with code from the two links above, could do the trick, but is that fired too often/would that have a malevolent impact on performance? If so, what would be a preferable event to hook, or would a timer be the way to go here?

这个代码，改编自下面约翰的例子（唯一的区别是计算器诱导基地电话。*被注释掉了，我改变了颜色从红色到黑色（以斯滕达尔没有提及意）），作品除了的，以前绘制的矩形松开鼠标后，再次显示。 IOW，第一个矩形绘制完美 - 用鼠标点击了（按预期）消失。然而，当我通过按下鼠标左键，再次拖累和权，的第一个的矩形显示器描述一个矩形！而这将继续发生。 - 每个的前面绘制的矩形被记住并带回时，正在制定一个新的矩形中脱颖而出

This code, adapted from John's example below (the only difference is the StackOverflow-inducing calls to base.* are commented out, and I changed the color from red to black (no reference to Stendahl intended)), works except that previously drawn rectangles display again after releasing the mouse. IOW, the first rectangle draws perfectly - it disappears with the mouse up click (as intended). However, when I describe a second rectangle by depressing the left mouse key and dragging down and to the right, the first rectangle displays again! And this continues to happen - every previously drawn rectangle is remembered and brought back to the fore when a new rectangle is being drawn.

公共部分Form1类：表格
{
私人点？ _开始;
私人矩形_previousBounds;

public partial class Form1 : Form { private Point? _start; private Rectangle _previousBounds;

public Form1()
{
    InitializeComponent();
}

private void Form1_MouseDown(object sender, MouseEventArgs e)
{
    _start = e.Location;
    //base.OnMouseDown(e); 

}

private void Form1_MouseMove(object sender, MouseEventArgs e)
{
    if (_start.HasValue)
        DrawFrame(e.Location);

    //base.OnMouseMove(e); 

}

private void Form1_MouseUp(object sender, MouseEventArgs e)
{
    ReverseFrame();
    _start = null;
    //base.OnMouseUp(e); 
}

private void ReverseFrame() 
{ 
    ControlPaint.DrawReversibleFrame(_previousBounds, Color.Black, FrameStyle.Dashed); 
} 

private void DrawFrame(Point end) 
{ 
    ReverseFrame(); 

    var size = new Size(end.X - _start.Value.X, end.Y - _start.Value.Y); 
    _previousBounds = new Rectangle(_start.Value, size); 
    _previousBounds = this.RectangleToScreen(_previousBounds); 
    ControlPaint.DrawReversibleFrame(_previousBounds, Color.Black, FrameStyle.Dashed); 
} 

}

}