.NET连接oracle实现用户登陆出问题

实现一个简单的用户登陆,数据来自Oracle数据库,代码如下,执行到readOracleDataReader reader = cmd.ExecuteReader()时出错。
单步看过用户名和密码都是正确的,哪里有问题呢?新手求教。

 protected void Button1_Click(object sender, EventArgs e)
    {
        String username = UserName.Text.ToString();
        String password = Password.Text.ToString();
        String queryString = "select CZR_MM,CZR_XM from T_BYSQ_BJSH_SKB_CZR where CZR_XM=@UserName and CZR_MM=@Password";
        // string connString = "DATA SOURCE=orcl;PERSIST SECURITY INFO=True;USER ID=SCOTT;password=admin";
        String connString = ConfigurationManager.ConnectionStrings["ConnectionStringUseOracleClient"].ToString();
        OracleConnection conn = new OracleConnection(connString);//连接oracle数据库
        try
        {
            conn.Open();//打开数据库,以便下面的操作
            Response.Write("数据库打开成功<br>");
            OracleCommand cmd= new OracleCommand();//创建一个OracleCommand对象,以便用它执行一个的语句/存储过程
            Response.Write("cmd对象创建成功<br>");
            cmd.Connection = conn;
            cmd.CommandText = queryString;
            cmd.Parameters.Add(new OracleParameter("@UserName",username));
            cmd.Parameters.Add(new OracleParameter("@Password", password));
            OracleDataReader reader = cmd.ExecuteReader();
            Response.Write("执行成功<br>");
            Response.Write(reader);
            Response.Write("连接成功<br>");
        }
        catch (Exception ex)
        {
            Response.Write("连接失败");
        }
        finally
        {
            conn.Close();
        }
   }
   

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