private void Form1_Load(object sender, EventArgs e)
        {
            this.textBox1.GotFocus+=new EventHandler(textBox1_GotFocus);
        }        void textBox1_GotFocus(object sender, EventArgs e)
        {
            textBox1.SelectAll();
            textBox1.Copy();
        }在textBox1获得焦点的事件中进行处理就可以了