C# 卡控时间输入

int hour = (int.Parse(DateTime.Now.Hour.ToString())) * 60;
        int minute = int.Parse(DateTime.Now.Minute.ToString());
        int nowTime = hour + minute;

int hour1 = (int.Parse(txthour.Text)) * 60;

int minute1 = (int.Parse(txtmin.Text));

int oldTime = hour1 + minute1;

if ((nowTime - oldTime) > 30)

　　{

　　　　lblMsg.Text = "登記時間應在當前時間的前30分鐘內！" ;
              lblMsg.ForeColor = System.Drawing.Color.Red;
              txthour.ForeColor = System.Drawing.Color.Red;
              txtmin.ForeColor = System.Drawing.Color.Red;
              return;

}

　　  else if ((nowTime - oldTime) < 0)

　　   {

　　　　  lblMsg.Text = "登記時間不應在當前時間之後！" ;
           　  lblMsg.ForeColor = System.Drawing.Color.Red;
                 txthour.ForeColor = System.Drawing.Color.Red;
                 txtmin.ForeColor = System.Drawing.Color.Red;
                 return ;

　　　}