ทำ Form Login บน Windows Form Application ง่าย ๆ ด้วย VB.NET และ C#

Imports System.Data.OleDb
Imports System.Data
Public Class frmLogin

    Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click

        Dim objConn As New OleDbConnection
        Dim objCmd As New OleDbCommand
        Dim strConnString, strSQL As String
        Dim directory As String = My.Application.Info.DirectoryPath

        strConnString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & directory & "\database.mdb;Jet OLEDB:Database Password=;"
        objConn.ConnectionString = strConnString
        objConn.Open()

        Dim intNumRows As Integer
        strSQL = "SELECT COUNT(*) FROM member WHERE Username = '" & Me.txtUsername.Text & "' AND [Password] = '" & Me.txtPassword.Text & "' "
        objCmd = New OleDbCommand(strSQL, objConn)
        intNumRows = objCmd.ExecuteScalar()

        If intNumRows > 0 Then
            Dim frm As New frmMain
            frm._strUser = Me.txtUsername.Text
            frm.LoadInfor()
            frm.Show()

            Me.Hide()
        Else
            MessageBox.Show("Username or Password Incorrect")
        End If

        objConn.Close()
        objConn = Nothing

    End Sub

    Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click
        If MessageBox.Show("Exit application?", "", MessageBoxButtons.YesNo) = DialogResult.Yes Then
            Application.Exit()
        End If
    End Sub


End Class

Imports System.Data.OleDb
Imports System.Data
Public Class frmMain

    Dim strUser As String

    Public Property _strUser() As String
        Get
            Return strUser
        End Get
        Set(ByVal value As String)
            strUser = value
        End Set
    End Property

    Public Sub LoadInfor()

        Dim objConn As New OleDbConnection
        Dim objCmd As New OleDbCommand
        Dim dtAdapter As OleDbDataAdapter
        Dim dt As New DataTable
        Dim strConnString, strSQL As String
        Dim directory As String = My.Application.Info.DirectoryPath


        strConnString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & directory & "\database.mdb;Jet OLEDB:Database Password=;"
        objConn.ConnectionString = strConnString
        objConn.Open()

        strSQL = "SELECT * FROM member WHERE Username = '" & strUser & "' "

        dtAdapter = New OleDbDataAdapter(strSQL, objConn)
        dtAdapter.Fill(dt)

        If dt.Rows.Count > 0 Then
            Me.lblUser.Text = strUser
            Me.lblName.Text = dt.Rows(0)("Name")
            Me.lblEmail.Text = dt.Rows(0)("Email")
        End If

        objConn.Close()
        objConn = Nothing
    End Sub

    Private Sub btnBack_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnBack.Click
        Dim frm As New frmLogin
        frm.Show()

        Me.Hide()
    End Sub
End Class

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
using System.IO;

namespace LoginFormCS
{
    public partial class frmLogin : Form
    {
        public frmLogin()
        {
            InitializeComponent();
        }

        private void btnLogin_Click(object sender, EventArgs e)
        {
            OleDbConnection objConn = new OleDbConnection();
            OleDbCommand objCmd = new OleDbCommand();
            string strConnString = null;
            string strSQL = null;
            string directory = Path.GetDirectoryName(Application.ExecutablePath);

            strConnString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + directory + "\\database.mdb;Jet OLEDB:Database Password=;";
            objConn.ConnectionString = strConnString;
            objConn.Open();

            int intNumRows = 0;
            strSQL = "SELECT COUNT(*) FROM member WHERE Username = '" + this.txtUsername.Text + "' AND [Password] = '" + this.txtPassword.Text + "' ";
            objCmd = new OleDbCommand(strSQL, objConn);
            intNumRows = Convert.ToInt32(objCmd.ExecuteScalar());

            if (intNumRows > 0)
            {
                frmMain frm = new frmMain();
                frm._strUser = this.txtUsername.Text;
                frm.LoadInfor();
                frm.Show();

                this.Hide();
            }
            else
            {
                MessageBox.Show("Username or Password Incorrect");
            }

            objConn.Close();
            objConn = null;
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            if (MessageBox.Show("Exit application?", "", MessageBoxButtons.YesNo) == DialogResult.Yes)
            {
                Application.Exit();
            }
        }


    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
using System.IO;

namespace LoginFormCS
{


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

        string strUser;
        public string _strUser
        {
            get { return strUser; }
            set { strUser = value; }
        }

        public void LoadInfor()
        {
            OleDbConnection objConn = new OleDbConnection();
            OleDbCommand objCmd = new OleDbCommand();
            OleDbDataAdapter dtAdapter = default(OleDbDataAdapter);
            DataTable dt = new DataTable();
            string strConnString = null;
            string strSQL = null;
            string directory = Path.GetDirectoryName(Application.ExecutablePath);


            strConnString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + directory + "\\database.mdb;Jet OLEDB:Database Password=;";
            objConn.ConnectionString = strConnString;
            objConn.Open();

            strSQL = "SELECT * FROM member WHERE Username = '" + strUser + "' ";

            dtAdapter = new OleDbDataAdapter(strSQL, objConn);
            dtAdapter.Fill(dt);

            if (dt.Rows.Count > 0)
            {
                this.lblUser.Text = strUser;
                this.lblName.Text = dt.Rows[0]["Name"].ToString();
                this.lblEmail.Text = dt.Rows[0]["Email"].ToString();
            }

            objConn.Close();
            objConn = null;
        }

        private void btnBack_Click(object sender, EventArgs e)
        {
        frmLogin frm = new frmLogin();
        frm.Show();
        this.Hide();
        }
    }
}

Imports System.Data.SqlClient
Imports System.Data
Public Class frmLogin

    Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click

        Dim objConn As New SqlConnection
        Dim objCmd As New SqlCommand
        Dim strConnString, strSQL As String

        strConnString = "Server=IP/Server;UID=sa;PASSWORD=;Database=database;Max Pool Size=400;Connect Timeout=600;"
        objConn.ConnectionString = strConnString
        objConn.Open()

        Dim intNumRows As Integer
        strSQL = "SELECT COUNT(*) FROM member WHERE Username = '" & Me.txtUsername.Text & "' AND [Password] = '" & Me.txtPassword.Text & "' "
        objCmd = New SqlCommand(strSQL, objConn)
        intNumRows = objCmd.ExecuteScalar()

        If intNumRows > 0 Then
            Dim frm As New frmMain
            frm._strUser = Me.txtUsername.Text
            frm.LoadInfor()
            frm.Show()

            Me.Hide()
        Else
            MessageBox.Show("Username or Password Incorrect")
        End If

        objConn.Close()
        objConn = Nothing

    End Sub

    Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click
        If MessageBox.Show("Exit application?", "", MessageBoxButtons.YesNo) = DialogResult.Yes Then
            Application.Exit()
        End If
    End Sub


End Class