Question

C#中两个picturebox控件，完全重合，上面的透明，怎么能实现单击上面某处的可以在下面的相应位置画圆啊

Answer 1

楼上的朋友的方法可以实现效果，但是个人认为将其中的PictureBox隐藏并不是很好的解决方案。我的方式是通过点击Pic2的时候，刷新Pic1，致使引发Pic1的Paint事件。然后通过一个Bool变量来判断是否需要进行绘制来达到效果。
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
PictureBox picDraw1 = new PictureBox();
PictureBox picDraw2 = new PictureBox();

private void Form1_Load(object sender, EventArgs e)
{
picDraw1.Size=new System.Drawing.Size(100,100);
picDraw1.BackColor=Color.Yellow;
picDraw1.Paint += new PaintEventHandler(picDraw1_Paint);
picDraw2.Size=new System.Drawing.Size(100,100);
picDraw2.BackColor=Color.Gray;
picDraw2.Location = new Point(100, 0);
picDraw2.Click += new EventHandler(picDraw2_Click);
this.Controls.Add(picDraw1);
this.Controls.Add(picDraw2);
}
bool isPic2Send = false;
void picDraw1_Paint(object sender, PaintEventArgs e)
{
if (isPic2Send)
{
e.Graphics.DrawEllipse(new Pen(Color.Green, 2), 10, 10, 30, 30);
}
}

void picDraw2_Click(object sender, EventArgs e)
{
isPic2Send = true;
picDraw1.Refresh();
}
}

Answer 2

貌似能用的隐藏控件的方法都会使控件失效，所以由题意，我写了个勉强算合要求的程序：
首先创建了两个重叠的PictureBox实例pictureBox1，pictureBox2，
pictureBox1位于pictureBox2底一层，在pictureBox2属性中设置visible为false
在InitializeComponent()中添加代码（默认在Form1.Designer.cs中）
this.pictureBox1.MouseDown += new System.Windows.Forms.MouseEventHandle (this.pictureBox1_MouseDown);
this.pictureBox2.MouseDown += new System.Windows.Forms.MouseEventHandler(this.pictureBox2_MouseDown);
在class Form1下添加代码：（默认在Form1.cs中）
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
pictureBox2_MouseDown(sender, e);
}

private void pictureBox2_MouseDown(object sender, MouseEventArgs e)
{
float Radius = 25; //圆半径值，可修改
pictureBox1.Image = new Bitmap(pictureBox1.Height, pictureBox1.Width);
Graphics g = Graphics.FromImage(pictureBox1.Image);
g.DrawEllipse(Pens.Black, new RectangleF(e.X - Radius, e.Y - Radius, 2 * Radius, 2 * Radius));
}
只能说，程序逻辑上的确完全是按您所述的要求来做的，虽然看着就觉得多此一举。。。
希望您的采纳~~