C#窗体淡入淡出

        //淡入
        public int state = 0;
private void f2_Load(object sender, EventArgs e)
        {
this.Opacity = 0;
        }  
private void timer1_Tick(object sender, EventArgs e)
        {
if (state == 0)
            {
this.Opacity += 0.02;
if (this.Opacity == 1)
                {
                    state = 1;
                    timer1.Enabled = false;
                }
            }
else
            {
this.Opacity = Opacity - 0.02;
if (this.Opacity == 0)
                {
                    Application.ExitThread();
                }
            }
        }
//退出
        private void f2closing(object sender, FormClosingEventArgs e)
        {
            e.Cancel = true;
            timer1.Start();
        }