private async void button1_Click(object sender, EventArgs e)

        {

            #region 单个执行的异步，效率慢

            HttpClient wc = new HttpClient();

            string s1 = await wc.GetStringAsync(textBox1.Text);

            label1.Text = s1.Length.ToString();

            string s2 = await wc.GetStringAsync(textBox2.Text);

            label2.Text = s2.Length.ToString();

            string s3 = await wc.GetStringAsync(textBox3.Text);

            label3.Text = s3.Length.ToString();

            #endregion

            #region 并发全部完成的异步更快

            HttpClient hc = new HttpClient();

            var task1 = hc.GetStringAsync(textBox1.Text);

            var task2 = hc.GetStringAsync(textBox2.Text);

            var task3 = hc.GetStringAsync(textBox3.Text);

            Task.WaitAll(task1, task2, task3);

            label1.Text = task1.Result.Length.ToString();

            label2.Text = task2.Result.Length.ToString();

            label3.Text = task3.Result.Length.ToString();

            #endregion

        }