reader对象绑定到RadioButtonList的默认选项的问题。

测试页面时，RadioButtonList1没有默认值。直接输出reader2["heart"]的值不为空。    protected void Page_Load(object sender, EventArgs e)
    {
        SqlConnection conn1 = new SqlConnection(ConfigurationManager.ConnectionStrings["BOZConnectionString"].ConnectionString);
        try
        {
            SqlCommand cmd1 = new SqlCommand("SELECT id, title, diary_time, heart FROM article WHERE (GUID = @GUID)", conn1);
            cmd2.Parameters.Add("@GUID",SqlDbType.UniqueIdentifier).Value = new Guid(Request.QueryString["GUID"]);
            conn1.Open();
            SqlDataReader reader1 = cmd1.ExecuteReader();
            while (reader1.Read())
            {
                TextBox1.Text = reader1["title"].ToString();
                TextBox2.Text = reader1["diary_time"].ToString();
                RadioButtonList1.SelectedValue = reader2["heart"].ToString();
                Response.Write(reader2["heart"].ToString());
            }
            reader1.Close();
        }        catch (Exception ex)
        {
            Response.Write(ex.Message);
        }        finally
        {
            conn1.Close();
        }
    }