[C#][coding] String.PadLeft();

        protected void btnRan_Click(object sender, EventArgs e)
        {
            Random ran = new Random();
            lblShow3.Text = "";
            lblShow3.Text += "祝您中大獎!";
            lblShow3.Text += "<hr>";
            for (int i = 1; i <= 5; i++ )
            {
                lblShow3.Text += "第" + i + "組:";
                for (int j = 0; j < 5; j++ )
                {
                    string v = Convert.ToString(ran.Next(1, 99));
                    lblShow3.Text += v.PadLeft(2, '0') + ", ";
                    if (j == 5)
                    {
                        lblShow3.Text += v.PadLeft(2, '0');
                        j++;
                    }
                    continue;
                }
                lblShow3.Text += "<br>";
            }
        }

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v = v.PadLeft(2, '0');
2:看要補幾位，
0:要用什麼值補那個位。
快去玩看看吧!

Ref: ASP .Net 4.0 從零開始 -使用C# 2010 (有興趣麻煩請參閱，僅供參考用，非打廣告，)