C#设置欢迎窗体由不透明变透明

        public Form1()
        {
            InitializeComponent();
        }

        private bool isForm1 = true;  //设置用于指示淡入淡出变化方向的变量

        private void Form1_Load(object sender, EventArgs e)
        {
            this.ClientSize = this.BackgroundImage.Size;      //设置欢迎的界面大小和背景的图片大小一致

            this.Opacity = 0;        //欢迎界面全透明

            this.timer1.Interval = 50;     //设置timer的时间间隔
            
            this.timer1.Enabled = true;     //使计时器开始运作

            this.timer1.Start();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            if (isForm1)
            {
                this.Opacity += 0.02;      //由不透明变成透明
                if (this.Opacity >= 1)      //当完全不透明时再由不透明变成透明
                {
                    isForm1 = false;
                }
            }
            else
            {
                this.Opacity -= 0.02;        //由透明转换为不透明
                if (this.Opacity <= 0)        //当完全透明时停止计时器，并退出欢迎界面
                {
                    this.timer1.Stop();
                    this.Close();
                }
            }
        }