编译错误,排错

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {

        SqlConnection conn = new SqlConnection("user id=test;password=aaa;database=pay;server=aaa-5ffb53b4342");
        SqlCommand cmd = new SqlCommand("Pay_SitePoint_GetPoint",conn);
        cmd.CommandType = CommandType.StoredProcedure;
        SqlParameter para = new SqlParameter();
        para.ParameterName = "@username";
        para.SqlDbType = SqlDbType.VarChar;
        para.Direction = ParameterDirection.Input;
        para.Value = TextBox1.Text.Trim();
        cmd.Parameters.Add(para);

        para.ParameterName = "@FreePoint";
        para.SqlDbType = SqlDbType.Decimal;
        para.Direction = ParameterDirection.Output;

        para.ParameterName = "@BuyPoint";
        para.SqlDbType = SqlDbType.Decimal;
        para.Direction = ParameterDirection.Output;

        conn.Open();
        SqlDataReader myDataReader = cmd.ExecuteReader();
        while (myDataReader.Read())
        {
            Response.Write(myDataReader.GetDecimal(0)+","+myDataReader.GetDecimal(0));
        }
        myDataReader.Close();
        conn.Close();
    }

}

编译提示:   过程或函数 'Pay_SitePoint_GetPoint' 需要参数 '@UserName'，但未提供该参数。
请帮忙找出错误.

功能就是调一个存储过程,输入一个参数.输出二个参数.

         --------------------编程问答--------------------

    protected void Button1_Click(object sender, EventArgs e)

    {

        SqlConnection conn = new SqlConnection("user id=test;password=aaa;database=pay;server=aaa-5ffb53b4342");

        SqlCommand cmd = new SqlCommand("Pay_SitePoint_GetPoint", conn);

        cmd.CommandType = CommandType.StoredProcedure;

        cmd.Parameters.AddWithValue("@UserName", TextBox1.Text.Trim());

        cmd.Parameters.Add("@FreePoint", SqlDbType.Decimal).Direction = ParameterDirection.Output;

        cmd.Parameters.Add("@BuyPoint", SqlDbType.Decimal).Direction = ParameterDirection.Output;



        conn.Open();

        SqlDataReader myDataReader = cmd.ExecuteReader();

        while (myDataReader.Read())

        {

            //下面有点问题,怎么下标都是0?

            Response.Write(myDataReader.GetDecimal(0) + "," + myDataReader.GetDecimal(0)); 

        }

        myDataReader.Close();

        conn.Close();

    }

补充：.NET技术 ,  ASP.NET