public Form1()
        {

　　　　InitializeComponent();  
            this.pictureBox1.Paint += new PaintEventHandler(pictureBox1_Paint);  
  }
void pictureBox1_Paint(object sender, PaintEventArgs e)  
        {  
            foreach (Control C in this.Controls)  
            {  
                if (C is Label)  
                {  
                    Label L = (Label)C;  
                    L.Visible = false;  
                    e.Graphics.DrawString(L.Text, L.Font, new 
          SolidBrush(L.ForeColor), L.Left - this.pictureBox1.Left, L.Top - this.pictureBox1.Top);  
                }  
            }  
        } 

用此代码虽然在pictureBox上实现了label的透明，但是在程序运行后label上面的字却看不见了，请教各位大侠是怎么回事？？？