Timer t1 = new Timer();
private void Form1_Load(object sender, EventArgs e)
{
Opacity = 0; //first the opacity is 0
t1.Interval = 10; //we'll increase the opacity every 10ms
t1.Tick += new EventHandler(fadeIn); //this calls the function that changes opacity
t1.Start();
}
void fadeIn(object sender, EventArgs e)
{
if (Opacity >= 1)
t1.Stop(); //this stops the timer if the form is completely displayed
else
Opacity += 0.05;
}