protected void ButtonStart_Click(object sender, EventArgs e)
        {
            string qnum, timenum, b;
            int a, i, j;

            //建立连接
            SqlConnection conn = new SqlConnection(ConfigurationSettings.AppSettings["connString"]);

            //打开连接
            conn.Open();


            //建立sql1字符串
            string sql1 = @"select * from denglubiao where usename='" + Session["usename"] + "'";

            //建立数据适配器
            SqlDataAdapter sda1 = new SqlDataAdapter(sql1, conn);

            //建立数据集
            DataSet ds1 = new DataSet();

            //填充数据集
            sda1.Fill(ds1, "denglubiao");
           
            foreach (DataRow row in ds1.Tables["denglubiao"].Rows)
            {
                qnum = row["tqnum"].ToString();
                timenum = row["ttimenum"].ToString();
            }
            i = Convert.ToInt32(qnum);   //这里的显示这样的错误“使用了未赋值的局部变量qnum”
            j = Convert.ToInt32(timenum);  //这里的错误和上面一样
            Random ro = new Random();
            a = ro.Next(i) + j;
            b = Convert.ToString(a);


            //建立sql字符串
            string sql = @"select * from Table1 order by UnitNum asc";
   
            //建立数据适配器
            SqlDataAdapter sda = new SqlDataAdapter(sql, conn);

            //建立数据集
            DataSet ds = new DataSet();

            //填充数据集
            sda.Fill(ds, "Table1");

            foreach (DataRow row in ds.Tables["Table1"].Rows)
            {
                if (row["QuestionNum"].ToString() == b)
                {
                    Label2.Text = b + ". " + row["Question"].ToString() + "<br>" + row["ChoiceA"].ToString() + "<br>" + row["ChoiceB"].ToString() + "<br>" + row["ChoiceC"].ToString() + "<br>" + row["ChoiceD"].ToString();
                }
            }
            conn.Close();
        }
我想把数据库中tqnum和ttimenum字段下的字符串型数据取出来赋值给定义好的变量，就出现了红色字体处的错误，让我很无解，请大侠们帮忙解决下，谢谢了

在定义string qnum, timenum, b;
            int a, i, j;后给这两个变量赋值为空字符串就可以了。

这样啊……我去试试，谢谢啊