how to write a 3layers winform applications in c#?

Question

how to write a 3layers winform applications in c#?

Farshad Valizade 501

hi every body

i am noob in c# and programming and i really care to code right and learn c# programming very correctly. so at first I want to write a 3 layers win form applications that read and write data into a table in sql server.

for this project I made 2 class and 1 form.

class DocumentDAL fro Data Layer

class DocumentBLL for Business Layer

winform for VIEW.

my codes:

DocumentDAL :


internal class DocumentDAL
    {
        private SqlConnection conn = new SqlConnection("Server=SQLSERVER.1;Integrated Security=SSPI;Persist Security Info=False;User ID=kiansaze;Initial Catalog=Karjoo;Data Source=DESKTOP-UKJISPV");
        internal int DocID;
        internal int DocRev;
        internal string DocTitle;

        public DataTable Select()
        { 
            string sqlcommand = "select * from Document";
            SqlDataAdapter da = new SqlDataAdapter(sqlcommand, conn);
            DataTable dt = new DataTable();
            da.Fill(dt);
            return dt;
        }

        public int Add()
        {
            string query = "insert into Document values(@doctitle,@docrev)";
            SqlCommand cmd = new SqlCommand(query, conn);
            cmd.Parameters.AddWithValue("@doctitle", this.DocTitle);
            cmd.Parameters.AddWithValue("@docrev", this.DocRev);
            int result = cmd.ExecuteNonQuery();
            return result;
        }
        public int Update()
        {
            string query = "update Document set doctitle = @doctitle,docrev=@docrev where docid = @docid";
            SqlCommand cmd = new SqlCommand(query, conn);
            cmd.Parameters.AddWithValue("@docid", this.DocID);
            cmd.Parameters.AddWithValue("@doctitle", this.DocTitle);
            cmd.Parameters.AddWithValue("@docrev", this.DocRev);
            int result = cmd.ExecuteNonQuery();
            return result;
        }
    }

DocumentBLL :

internal class DocumentBLL
    {
        private DocumentDAL _docDal ;

        public  int DocID { get; set; }
        public int DocRev { get; set; }
        public string DocTitle { get; set; }

        public DataTable Select()
        {
            _docDal = new();
            return _docDal.Select();
        }

        public bool Add()
        {
            _docDal = new();
            if (_docDal.Add() > 0)
                return true;
            else
                return false;

        }
        public bool Update()
        {
            _docDal = new();
            if (_docDal.Update() > 0)
                return true;
            else
                return false;
        }


    }

Form:

 public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnAdd_Click(object sender, EventArgs e)
        {
            DocumentBLL documentBLL = new DocumentBLL();
            documentBLL.DocTitle = txtDocTitle.Text;
            documentBLL.DocRev = int.Parse(txtDocRev.Text);
            if (documentBLL.Add())
            {
                MessageBox.Show("Add Success");
            }
        }

        private void btnEdit_Click(object sender, EventArgs e)
        {
            DocumentBLL documentBLL = new DocumentBLL();
            documentBLL.DocID = int.Parse(dataGridView1.SelectedRows[0].Cells["DocID"].Value.ToString());
            documentBLL.DocTitle = txtDocTitle.Text;
            documentBLL.DocRev = int.Parse(txtDocRev.Text);
            if (documentBLL.Update())
            {
                MessageBox.Show("Update Success");
            }
        }

        private void btnSelect_Click(object sender, EventArgs e)
        {
            DocumentBLL documentBLL = new DocumentBLL();
            dataGridView1.DataSource = documentBLL.Select();
        }
    }

I do this but didn't know is it true coding or not?

Are DocumentDAL and DocumentBLL class Right?

Please check my code and tell me is this way of programming 3layers rights?

0 comments

3 answers

Your answer

Answer 1

Hi,@Farshad Valizade . Welcome Microsoft Q&A.

For the three layers winform project, you could try the following example.

Form1.cs:

using WinFormsApp1.BLL;
using WinFormsApp1.DAL;
namespace WinFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
          
        }
  
        private void btnAdd_Click(object sender, EventArgs e)
        {
            DocumentHandler documentH = new DocumentHandler();
            if (documentH.InsertDocument(new DAL.Document() { DocRev = int.Parse(txtDocRev.Text), DocTitle = txtDocTitle.Text, DocID= int.Parse(txtDocId.Text) }))
            {
                MessageBox.Show("Add Success");
                dataGridView2.DataSource = documentH.GetDocuments();
            }
            
        }
        private void dataGridView2_SelectionChanged(object sender, EventArgs e)
        {
            if (dataGridView2.SelectedRows.Count > 0) // make sure user select at least 1 row 
            {
                string Id = dataGridView2.SelectedRows[0].Cells[0].Value + string.Empty;
                string Rev = dataGridView2.SelectedRows[0].Cells[1].Value + string.Empty;
                string Title = dataGridView2.SelectedRows[0].Cells[2].Value + string.Empty;
                txtDocId.Text = Id;
                txtDocTitle.Text = Title;
                txtDocRev.Text = Rev;
            }
        }
        private void btnEdit_Click(object sender, EventArgs e)
        {
            DocumentHandler documentH = new DocumentHandler();
            if (documentH.UpdateDocument(new DAL.Document() { DocRev = int.Parse(txtDocRev.Text), DocTitle = txtDocTitle.Text,
                DocID = int.Parse(txtDocId.Text)
            }))
            {
                MessageBox.Show("Add Success");
                dataGridView2.DataSource = documentH.GetDocuments();
            }
          
        }
        private void btnSelect_Click(object sender, EventArgs e)
        {
            try
            {
                DocumentHandler d = new DocumentHandler();
                this.dataGridView2.DataSource = d.GetDocuments(Convert.ToInt16(this.txtID.Text));
            }
            catch
            {
                MessageBox.Show("Error Occurred");
            }
        }
      
        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {
                
               
                DocumentHandler d = new DocumentHandler();
                this.dataGridView2.DataSource = d.GetDocuments();
            }
            catch
            {
                MessageBox.Show("Error Occurred");
            }
        }
    
    }
}

BLL:

using System.Data;
using WinFormsApp1.DAL;
using Document = WinFormsApp1.DAL.Document;
namespace WinFormsApp1.BLL
{
   
    public class DocumentHandler
    {
        public DataTable GetDocuments()
        {
            try
            {
                DocumentDAL objdal = new DocumentDAL();
                return objdal.Read();
            }
            catch
            {
                throw;
            }
        }
        public DataTable GetDocuments(Int16 ID)
        {
            try
            {
                DocumentDAL objdal = new DocumentDAL();
                return objdal.Read(ID);
            }
            catch
            {
                throw;
            }
        }
        public bool InsertDocument(Document document)
        {
            if (DocumentDAL.Validate(document))
            {
                DocumentDAL.Add(document);
                return true;
            }
            return false;
        }
        public bool UpdateDocument(Document document)
        {
            if (DocumentDAL.Validate(document))
            {
                DocumentDAL.Update(document);
                return true;
            }
            return false;
        }
    }
   
}

DAL:


using System.Data;
using System.Data.SqlClient;

namespace WinFormsApp1.DAL
{
   
    public  class Document
    {
        public int DocID { get; set; }
        public int DocRev { get; set; }
        public string DocTitle { get; set; }
    }
    internal class DocumentDAL
    {
        public static string ConString = "constr";
        static SqlConnection conn = new SqlConnection(ConString);
       
        DataTable dt = new DataTable();
        public DataTable Read()
        {

            if (ConnectionState.Closed == conn.State)
                conn.Open();
            SqlCommand cmd = new SqlCommand("select * from [dbo].[Document]", conn);
          
            try
            {
                SqlDataReader rd = cmd.ExecuteReader();
                dt.Load(rd);
                return dt;
            }
            catch
            {
                throw;
            }
        }
        public DataTable Read(Int16 Id)
        {

            if (ConnectionState.Closed == conn.State)
                conn.Open();
            SqlCommand cmd = new SqlCommand("select * from Person where ID= " + Id + "", conn);
            try
            {
                SqlDataReader rd = cmd.ExecuteReader();
                dt.Load(rd);
                return dt;
            }
            catch
            {
                throw;
            }
        }
        public DataTable Select()
        {

            if (ConnectionState.Closed == conn.State)
                conn.Open();
            string sqlcommand = "select * from [dbo].[Document]";
            SqlDataAdapter da = new SqlDataAdapter(sqlcommand, conn);
            DataTable dt = new DataTable();
            da.Fill(dt);
            return dt;
        }

        public static void  Add(Document d)
        {
            if (ConnectionState.Closed == conn.State)
                conn.Open();
            string query = "insert into [dbo].[Document]([DocID],[DocTitle],[DocRev]) values(@docid, @doctitle,@docrev)";
            SqlCommand cmd = new SqlCommand(query, conn);
            cmd.Parameters.AddWithValue("@docid", d.DocID);
            cmd.Parameters.AddWithValue("@doctitle", d.DocTitle);
            cmd.Parameters.AddWithValue("@docrev", d.DocRev);
            cmd.ExecuteNonQuery();
           
        }
        public static void Update(Document d)
        {
            if (ConnectionState.Closed == conn.State)
                conn.Open();
            string query = "update [dbo].[Document] set DocTitle = @doctitle,DocRev=@docrev where DocID = @docid";
            SqlCommand cmd = new SqlCommand(query, conn);
            cmd.Parameters.AddWithValue("@docid", d.DocID);
            cmd.Parameters.AddWithValue("@doctitle", d.DocTitle);
            cmd.Parameters.AddWithValue("@docrev", d.DocRev);
            cmd.ExecuteNonQuery();
           
        }
        internal static bool Validate(Document d)
        {
            return true;
            // some validations before insert 
        }
    }
}

The result:

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Hui Liu-MSFT 48,711 Reputation points Microsoft External Staff

2023-01-30T08:13:52.68+00:00

Hi,@Farshad Valizade . Is there any update to the question? Did my answer solve your problem? If so, you could accept it as the answer. It's helpful for community members with related questions.
Farshad Valizade 501 Reputation points

2023-02-04T09:56:45.77+00:00

tnx very much i am using this code in my project but i have some questions:

1:in DAL in Read(int16 id) can id change it to Read(Document d) and in cmd parameter use d.DocID instead?

2: in Form class (view) can i use this code and prevent from duplicate use of _doc class in my method and use one instance of it and fill it in every method that i need?

public partial class Form1 : Form { DocumentBLL _docbll = new(); Document _doc = new(); public Form1() { InitializeComponent(); }

Answer 2

Bruce (SqlWork.com) 84,071

proper laying would make each layer a project with unit tests.

also not keen about the DAL & BLL layers returning datatables rather than POCO objects or records.

0 comments

Answer 3

Bruce (SqlWork.com) 84,071

duplicate post

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how to write a 3layers winform applications in c#?

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