很究诘的代码...怎么能写到在外类调用,,,,希望大家明白我说什么?哎........(修改1)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;

namespace sql_str {
    public class sql_str {
        public DataSet myds(SqlCommand return_com) {
            sql_db.db db_str = new sql_db.db();
            SqlConnection mycon = new SqlConnection(db_str.db_str());
            SqlDataAdapter da = new SqlDataAdapter(return_com);
            return_com.Connection = mycon;
            mycon.Open();
            DataSet ds = new DataSet();
            da.Fill(ds);
            return ds;
        }
        public DataSet methods_ds(string methods_name, user my_user) {
            SqlCommand mycom = new SqlCommand();
            switch (methods_name) {
                case "1":
                    mycom.CommandText = "select f_id from t_htmltable where f_id = @id";
                    break;
                case "2":
                    mycom.CommandText = "select f_name from t_htmltable where f_name = @name";
                    break;
                case "3":
                    mycom.CommandText = "select f_text from t_htmltable where f_text = @text";
                    break;
                case "4":
                    mycom.CommandText = "select * from t_htmltable where f_text = @text and f_id = @id";
                    break;
            }
            SqlParameter mypara_id = new SqlParameter("@id", SqlDbType.Int);
            SqlParameter mypara_name = new SqlParameter("@name", SqlDbType.VarChar);
            SqlParameter mypara_text = new SqlParameter("@text", SqlDbType.VarChar);
            mypara_id.Value = my_user.Id;
            mypara_name.Value = my_user.Name;
            mypara_text.Value = my_user.Text;
            mycom.Parameters.Add(mypara_id);
            mycom.Parameters.Add(mypara_name);
            mycom.Parameters.Add(mypara_text);
            return myds(mycom);
        }
        public DataSet return_ds() {
            user my_user = new user("f_id", 1);
            return methods_ds("1", my_user);
        }
    }
    public class user {
        int id = 0;
        string name = "";
        string text = "";
        public int Id {
            set { this.id = value; }
            get { return this.id; }
        }
        public string Name {
            set { this.name = value; }
            get { return this.name; }
        }
        public string Text {
            set { this.text = value; }
            get { return this.text; }
        }
        public user() {

        }
        public user(string variable_name, int variable_value) {
            switch (variable_name) {
                case "f_id":
                    this.id = variable_value;
                    break;
            }
        }
        public user(string variable_name, string variable_value) {
            switch (variable_name) {
                case "f_name":
                    this.name = variable_value;
                    break;
                case "f_text":
                    this.text = variable_value;
                    break;
            }
        }
    }
}