Short Answer:
You can't.
Real World Solution:
Have you looked into WPF?
Long Answer:
Opacity is a trick that WinForms does.
When a control is marked to be displayed transparent (or semi transparent), WinForms queries the parent object's visuals to ask "What would you have printed here had my control not existed?". From this result WinForms either displays the pixel of the control, the pixel of the parent, or a combination of the two (if semi transparent).
This becomes really apparent in a simple example:
- Create a new winforms project
- Create 2 labels, place them over top of each other (slighty offset)
- Set both labels backgrounds to
Color.Transparent
You'll see immediately that transparency takes a chunk out of the label underneath.
Example Code (All in one file, compile and run):
using System;
using System.Windows.Forms;
using System.Drawing;
namespace WindowsFormsApplication5
{
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new MainForm());
}
}
public class MainForm : Form
{
private Random random = new Random();
private Button btnRandomBackgroundColor;
private Label lblBackgroundLabel;
private Label lblTransparent;
public MainForm()
{
InitializeComponent();
}
private void button_Click(object sender, EventArgs e)
{
BackColor = Color.FromArgb(random.Next(0, 255),
random.Next(0, 255),
random.Next(0, 255));
}
private void InitializeComponent()
{
this.btnRandomBackgroundColor = new System.Windows.Forms.Button();
this.lblBackgroundLabel = new System.Windows.Forms.Label();
this.lblTransparent = new System.Windows.Forms.Label();
this.SuspendLayout();
//
// btnRandomBackgroundColor
//
this.btnRandomBackgroundColor.Location = new System.Drawing.Point(12, 12);
this.btnRandomBackgroundColor.Name = "btnRandomBackgroundColor";
this.btnRandomBackgroundColor.Size = new System.Drawing.Size(144, 23);
this.btnRandomBackgroundColor.TabIndex = 0;
this.btnRandomBackgroundColor.Text = "Randomize Background Color";
this.btnRandomBackgroundColor.UseVisualStyleBackColor = true;
this.btnRandomBackgroundColor.Click += button_Click;
//
// lblBackgroundLabel
//
this.lblBackgroundLabel.AutoSize = true;
this.lblBackgroundLabel.BackColor = System.Drawing.Color.Transparent;
this.lblBackgroundLabel.Font = new System.Drawing.Font("Microsoft Sans Serif", 21.75F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
this.lblBackgroundLabel.Location = new System.Drawing.Point(41, 49);
this.lblBackgroundLabel.Name = "lblBackgroundLabel";
this.lblBackgroundLabel.Size = new System.Drawing.Size(184, 33);
this.lblBackgroundLabel.TabIndex = 1;
this.lblBackgroundLabel.Text = "Simple Label";
//
// lblTransparent
//
this.lblTransparent.AutoSize = true;
this.lblTransparent.BackColor = System.Drawing.Color.Transparent;
this.lblTransparent.Font = new System.Drawing.Font("Microsoft Sans Serif", 21.75F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
this.lblTransparent.Location = new System.Drawing.Point(61, 63);
this.lblTransparent.Name = "lblTransparent";
this.lblTransparent.Size = new System.Drawing.Size(251, 33);
this.lblTransparent.TabIndex = 2;
this.lblTransparent.Text = "Transparent Label";
//
// Form1
//
this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.BackColor = System.Drawing.Color.White;
this.ClientSize = new System.Drawing.Size(341, 114);
Controls.Add(this.lblTransparent);
this.Controls.Add(this.lblBackgroundLabel);
this.Controls.Add(this.btnRandomBackgroundColor);
this.Name = "Form1";
this.Text = "MainForm";
this.ResumeLayout(false);
this.PerformLayout();
}
}
}
