checkboxlist传值问题急在线等

做了一个试题生成系统选择checkboxlist中的多道试题然后点击添加到试卷  生成试卷，会输出一个word
两个按钮一个添加一个生成，questionbanktb是数据库，courses是上个页面选择的科目
public partial class manual_select : System.Web.UI.Page
{
    string myString = "";
    protected void Page_Load(object sender, EventArgs e)
    {
        string courses = Request.QueryString["courses"];

        string str = "select * from questionbanktb where coursename='" + courses + "' ";
        conn db5 = new conn();
        System.Data.SqlClient.SqlDataReader datas5 = db5.exceutereader(str);
        this.CheckBoxList1.DataSource = datas5;
        this.CheckBoxList1.DataTextField = "question";
        this.CheckBoxList1.DataValueField = "id";
        this.CheckBoxList1.DataBind();
        datas5.Close();

    }
    protected void Submit1_ServerClick(object sender, EventArgs e)
    {
         System.Text.StringBuilder builder = new System.Text.StringBuilder();

        for (int i = 0; i < CheckBoxList1 .Items .Count ; i++)
        {
            if (CheckBoxList1 .Items [i].Selected ==true )
            {
                builder.AppendLine (CheckBoxList1 .Items [i].Text  );
                builder.AppendLine ("@");
             }
        }
        myString=builder.ToString();
}
    protected void Submit2_ServerClick(object sender, EventArgs e)
    {

        string numsingle = "";
        for (int i = 0; i < myString.Length; i++)
        {
            if (!myString.Substring(i, 1).Equals("@"))
            {
                numsingle = numsingle + myString.Substring(i, 1);
            }
            else
            {
                numsingle = numsingle + "\n";
            }
        }




        OutPut("attachment;filename=peper.doc", "application/ms-word", numsingle);
}
     private void OutPut(string fileType, string strType, String text)
    {
        Response.Clear();
        Response.Buffer = true;
        Response.Charset = "GB2312";
        Response.AppendHeader("Content-Disposition", fileType);
        Response.ContentType = strType;
        this.EnableViewState = false;
        Response.Write(text);
        Response.End();
    }
}
不知道为什么输出的word是空白的  哪位大侠教教我啊
其中conn类定义为
public class conn
{
    SqlConnection con = null;
    SqlCommand cmd = new SqlCommand();
    public conn()
    {
        //
        // TODO: 在此处添加构造函数逻辑
        //
        con = new SqlConnection("SERVER=.;uid=sa;pwd=1234;database=questionbank;");
    }
    public SqlConnection getconn()
    {
        if (con.State == ConnectionState.Closed)
            con.Open();
        return con;
    }
    public void clear()
    {
        if (con.State == ConnectionState.Open)
        {
            con.Close();
        }
    }
    public SqlDataReader exceutereader(string sql)
    {
        cmd.Connection = getconn();
        cmd.CommandText = sql;
        SqlDataReader str = cmd.ExecuteReader();
        return str;
    }
    public string exceutescalar(string sql)
    {
        string str = "";
        try
        {
            cmd.Connection = getconn();
            cmd.CommandText = sql;
            str = cmd.ExecuteScalar().ToString();
            clear();
        }
        catch (Exception e)
        {
            e.GetHashCode();
        }
        return str;
    }
    public void excuteupdate(string sql)
    {
        cmd.Connection = getconn();
        cmd.CommandText = sql;
        cmd.ExecuteNonQuery();
        clear();
    }
}


--------------------编程问答-------------------- 单步跟踪查看值
public string myString
{
get{return ViewState["myString"].ToString();}
set{ViewState["myString"]=value;}
} --------------------编程问答-------------------- 是把一开始的string myString = "";改成
public string myString
{
get{return ViewState["myString"].ToString();}
set{ViewState["myString"]=value;}
}吗？
还是不对啊
word还是空白的

补充：.NET技术 ,  ASP.NET

checkboxlist传值问题 急 在线等

checkboxlist传值问题急在线等