Using PostgreSQL to achieve layer three (review)

Modal dal,bll are all forms of class libraries

The final result is as follows:

Database code:

--table:student--DROP Table student; CREATE TABLE Student (  name text NOT NULL,  ' number ' integer NOT NULL,  telephone text,  CONSTRAINT "primary Key "PRIMARY key (name))

Insert

INSERT into Student values (' eldest ', 20, ' 12121212 ')

First, establish 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;}}    }

Second, SqlHelper (question: I put server=127.0.0.1; port=5432; User Id=postgres; password=123456;database=student; Uninstall app. config inside, but can't read it like MSSQL)

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 Rea DOnly 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>//Get all data----modal///</summary>//<param name= "SQL" >sql statements </pa ram>//<param name= "parameters" > Parameters </param>//<returns> Model </returns> Pub Lic list<studentmodal> getallstudentinfo (String sql,params npgsqlparameter[] parameters) {using (N Pgsqlconnection 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);                    Reading data from a DataTable to form 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"]);//needs to be handled as int student. Telephone = datatable.rows[i]["Telephone"].  ToString ();                      Studentlist.add (student);                } return studentlist;     }}}////converted to object or null//private object Fromdbvalue (This object obj)//{// return obj = = DBNull.Value?        Null:obj; }/////<summary>/////converted to null values in the database/////</summary>/////<param name= "obj        "></param>/////<returns></returns>//private Object Todbvalue (This object obj) {//return obj = = null?        DBNull.Value:obj; //}    }}

Third, DAL

Using system;using system.collections.generic;using system.linq;using system.text;using Mono.Security;using Studentmodal;namespace dal{public class Getstudentinfo {//<summary>///        Build SQL statements and get data //        </summary>        String sql = "SELECT * from";        Public list<studentmodal> Getallstudentinfodal (string dataTable)        {            Studentmodal.studenthelper Studenthelper = new Studenthelper ();            Return Studenthelper.getallstudentinfo (sql+datatable);}}    

Four, the 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>//////        from the Dal to get the required data for UI calls//</summary>//        <returns></returns> Public        list<studentmodal> GETSTUDENTLISTBLL ()        {            DAL. Getstudentinfo studentinfo = new Getstudentinfo ();            Return Studentinfo.getallstudentinfodal (dataTable);}}            }

V. 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);            }        }

Using PostgreSQL to achieve layer three (review)