用PostGreSQL实现三层(复习)

modal DAL，BLL都是类库的形式

最终结果如下：

数据库代码：

-- Table: student

-- DROP TABLE student;

CREATE TABLE student
(
  name text NOT NULL,
  "number" integer NOT NULL,
  telephone text,
  CONSTRAINT "primary key" PRIMARY KEY (name)
)

插入

INSERT INTO Student values('老大',20,'12121212')

一、先建立modal

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

namespace StudentModal
{
    public class studentModal
    {
        public string Name { get; set; }
        public int Number { get; set; }
        public string TelePhone { get; set; }
    }
}

二、sqlhelper(问题：我把Server=127.0.0.1;Port=5432;User Id=postgres;Password=123456;Database=STUDENT;卸载app.config里面，却不能像mssql一样读取到)

using Npgsql;

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Text;
using Mono.Security;

namespace StudentModal
{
    
    public class studentHelper
    {
        //private static readonly string conStr = ConfigurationManager.ConnectionStrings["conSQL"].ToString();
        private static readonly string conStr = "Server=127.0.0.1;Port=5432;User Id=postgres;Password=123456;Database=STUDENT;";
        private List<studentModal> studentList = new List<studentModal>();
        //private string sql = "select * from Student";
        /// <summary>
        /// 得到所有数据----modal
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="parameters">参数</param>
        /// <returns>模型</returns>
        public List<studentModal> getAllStudentInfo(string sql,params NpgsqlParameter[] parameters)
        {
            using(NpgsqlConnection con=new NpgsqlConnection(conStr))
            {
                con.Open();
                using (NpgsqlCommand cmd =new NpgsqlCommand())
                {
                    cmd.Connection = con;
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    NpgsqlDataAdapter adapter = new NpgsqlDataAdapter(cmd);
                    DataSet dataSet = new DataSet();
                    adapter.Fill(dataSet);
                    //从dataTable中读取数据形成modal
                    DataTable dataTable=dataSet.Tables[0];
                    int tableRow = dataTable.Rows.Count;
                    for (int i = 0; i < tableRow; i++)
                    {
                        studentModal student = new studentModal();
                        student.Name = dataTable.Rows[i]["Name"].ToString();
                        student.Number =Convert.ToInt32( dataTable.Rows[i]["Number"]);//需要处理为int
                        student.TelePhone = dataTable.Rows[i]["TelePhone"].ToString();
                        studentList.Add(student);
                    }
                    return studentList;
                }
            }
        }

        ////转换为object或者为空
        //private object FromDBValue(this object obj)
        //{
        //    return obj == DBNull.Value ? null : obj;
        //}
        ///// <summary>
        ///// 转换为数据库中的null值
        ///// </summary>
        ///// <param name="obj"></param>
        ///// <returns></returns>
        //private object ToDBValue(this object obj)
        //{
        //    return obj == null ? DBNull.Value : obj;
        //}

    }
}

三、DAL

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

using Mono.Security;
using StudentModal;

namespace DAL
{
    public class GetStudentInfo
    {
        /// <summary>
        /// 构建sql语句，然后得到数据
        /// </summary>
        string sql = "select * from ";
        public List<studentModal> GetAllStudentInfoDAL(string dataTable)
        {
            StudentModal.studentHelper studentHelper = new studentHelper();
            return studentHelper.getAllStudentInfo(sql+dataTable);
        }
    }
}

四、BLL

using DAL;
using StudentModal;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BLL
{
    public class StudentBLL
    {
        private string dataTable = "Student";
        /// <summary>
        /// 从DAL中得到所需数据，供UI调用
        /// </summary>
        /// <returns></returns>
        public List<studentModal> GetStudentListBLL()
        {
            DAL.GetStudentInfo studentInfo = new GetStudentInfo();
            return studentInfo.GetAllStudentInfoDAL(dataTable);
        }
        
    }
}

五、UI

        private void button1_Click(object sender, EventArgs e)
        {
            List<studentModal> studentListBLL = new List<studentModal>();
            BLL.StudentBLL studentBLL = new BLL.StudentBLL();
            studentListBLL= studentBLL.GetStudentListBLL();
            dataGridView1.Rows.Add(studentListBLL.Count);
            for (int j = 0; j < studentListBLL.Count; j++)
            {
                studentModal studentModal = studentListBLL[j];
                dataGridView1.Rows[j].Cells[0].Value = studentModal.Name;
                dataGridView1.Rows[j].Cells[1].Value = studentModal.Number;
                dataGridView1.Rows[j].Cells[2].Value = studentModal.TelePhone;
                //dataGridView1.Rows.Add(1);
            }
        }