提交试题代码。始终不能判断选择题，判断题没有错。原因在哪里？

Question

//交卷按钮代码
    protected void btnjj_Click(object sender, EventArgs e)
    { 
        //判断
        string sql = "select strRight_answer from jp_exam_hy where type_t='判断题' ";
        SqlDataAdapter dataAdapter = new SqlDataAdapter(sql, conn);
        DataSet dataset = new DataSet();
        dataAdapter.Fill(dataset, "jp_exam_hy");
        DataTable datatable = dataset.Tables["jp_exam_hy"];
        int c = 0;//存答正确答案
        for (int a = 0; a < GridView1.Rows.Count; a++)
        {            RadioButtonList rbl = (RadioButtonList)(GridView1.Rows[a].FindControl("rbanswer"));//取用户所选答案
            Label lblc = (Label)(GridView1.Rows[a].FindControl("lblc"));
            if (rbl != null && rbl.SelectedValue != "")
            {                string answer = datatable.Rows[a]["strRight_answer"].ToString().Trim();//取正确答案                if (rbl.SelectedValue.ToString().Trim() == answer)//比较
                {
                    c = c + 1;
                    lblc.Text = answer;
                    lblc.ForeColor = System.Drawing.Color.Blue;                 }
                else
                {
                    lblc.Text = answer;
                    lblc.ForeColor = System.Drawing.Color.Red; 
                }
            }        } //判断
        string sql1 = "select strRight_answer from jp_exam_hy where type_t='单项选择题' ";
        SqlDataAdapter dataAdapter1 = new SqlDataAdapter(sql1, conn);
        DataSet dataset1 = new DataSet();
        dataAdapter.Fill(dataset1, "jp_exam_hy");
        DataTable datatable1 = dataset1.Tables["jp_exam_hy"];
        int n = 0;//存答正确答案
        for (int b = 0; b < GridView2.Rows.Count; b++)
        {            RadioButtonList rbl1 = (RadioButtonList)(GridView2.Rows[b].FindControl("xbanswer"));//取用户所选答案
            Label lblb = (Label)(GridView2.Rows[b].FindControl("lblb"));
            if (rbl1 != null && rbl1.SelectedValue != "")
            {                string answer1 = datatable.Rows[b]["strRight_answer"].ToString().Trim();//取正确答案                if (rbl1.SelectedValue.ToString().Trim() == answer1)//比较
                {
                    n = n + 1;
                    lblb.Text = answer1;
                    lblb.ForeColor = System.Drawing.Color.Blue;                }
                else
                {
                    lblb.Text = answer1;
                    lblb.ForeColor = System.Drawing.Color.Red;
                }
            }        } 
        btnjj.Enabled = false;//交完一次就不能在交     
        c = c + n;
        Response.Write("<script>alert('一共90题！" + "  回答正确" + n + "题。 " + "得分" + c + "分。');</script>");    }

Answer 1

          int c = 0;//存答正确答案  判断题计数
            int n = 0;//存答正确答案  选择题计数        c = c + n; // 如果是 1题 1分 可以直接加 
        Response.Write(" <script>alert('一共90题！" + "  回答正确" + c + "题。 " + "得分" + c + "分。'); </script>"); 

Answer 2

最后是这样解决的。 //交卷按钮代码
    protected void btnjj_Click(object sender, EventArgs e)
    {
        int score = 0;
        string str = "";       
        foreach (GridViewRow dr in GridView1.Rows)//对单选题每题进行判断用户选择答案
        {
                     
            str = ((RadioButtonList)dr.FindControl("xbanswer")).Text.ToString();           
            if (str != "")
            {
                if (((Label)dr.FindControl("lblb")).Text.Trim() == str)//将用户选择结果和答案进行比较
                {
                    // 记录分数
                    score = score + 1;
                  
                }
            }
        }
        Response.Write("<script language=javascript>alert('您的成绩为：" + score + "分！')</script>");
    }