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How to check if user is log in once enter a form using c# winform only, no asp.netc#

NO asp.net c# used
I need to know if user is login once he/she enter a form and if he/she is not login, he goes back to the login form. Everywhere I saw people use asp.net to achieve that but I want to know how to do it without using asp.net.
public DataTable Login(String Username, String Password)
{
server = "localhost";
database = "xxxx";
uid = "root";
password = "";
string MySQLConnectionString = $"datasource=127.0.0.1;port = 3306; SERVER={server}; DATABASE={database}; USERNAME={uid}; PASSWORD={password};sslmode=none";
MySqlConnection db_Conn = new MySqlConnection(MySQLConnectionString);
MySqlCommand cmd = new MySqlCommand();
db_Conn.ConnectionString = MySQLConnectionString;
string username_txtfield = username_txtbox.Text;
string pw_txtfield = password_txtbox.Text;
try
{
db_Conn.Open();
cmd.Connection = db_Conn;
cmd.CommandText = "SELECT count(*),user_id,person_username,role_id FROM user_tb " +
"WHERE person_username=#username " +
"AND user_password=#password";
cmd.Prepare();
cmd.Parameters.AddWithValue("#username", username_txtfield);
cmd.Parameters.AddWithValue("#password", pw_txtfield);
MySqlDataReader dr = cmd.ExecuteReader();
DataTable dt = new DataTable();
dt.Load(dr);
db_Conn.Close();
return dt;
}
catch (Exception ex)
{
throw ex;
}
}
login btn in my login form
private void button1_Click(object sender, EventArgs e)
{
//login();
try
{
DataTable result = Login(username_txtbox.Text, password_txtbox.Text);
if (result.Rows.Count == 1)
{
this.Hide();
string role = result.Rows[0]["role_id"].ToString();
switch (role)
{
case "3":
MessageBox.Show("User login successfully!");
user_form_page();
break;
case "1":
MessageBox.Show("Admin login successfully!");
//this.Hide();
Admin_page admin_form = new Admin_page();
admin_form.ShowDialog();
this.Close();
break;
}
}
else
{
MessageBox.Show("INVALID USERNAME OR PASSWORD");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}

Of course the ASP.Net identity services is a mature way of doing such a task but if you want you can have your own method of authentication but, you will need to implement many things.
Many of the stuff you need is actually based on the scenario you are implementing but the most basic thing you need is a static user that will be used via your methods to see if the user is already logged in or not. For example you can have:
public static class Authentication
{
public static User CurrentUser { get; private set; }
public static bool Login(User user)
{
if(user == null)
throw new ArgumentException("Invalid user","user");
CurrentUser = user;
}
}
This is just the most basic implementation of such a thing you can then check if CurrentUser is null or not and direct user to login page or show her the results.
As your requirements grow you will need to implement more stuff. A logout, a local or remote database for users, store currently logged in user in disk so that she doesn't need to login again after closing the app and many other things
Edit
Based on your new information you can add this line to your login button click like this:
if (result.Rows.Count == 1)
{
Authentication.Login(new User(result.Rows[0]["username"],result.Rows[0]["role_id"])
//The rest of code
}
I have also presumed that you have a class like:
class User
{
public string Name { get; }
public int RoleId { get; }
public User(string name, int roleId)
{
Name = name;
RoleId = roleId;
}
}
And then you have to check Authentication.CurrentUser against null in your user form or admin form constructors to ensure user is login you can use the information in Authentication.CurrentUser to show logged in user name or role or any other info.
I hope this helps you. If you need more info please say so.

My File accdb is missing but Data still can entry

In my C# apps "MyApps.Exe", i use Provider Microsoft.ace.oledb.12.0 to access my accdb file..
I set data source with
Data Source="+Application.StartupPath+"\\databaseFile.accdb
So my apps will read the databaseFile.accdb in the same folder with Exe file. The folder name is CurrentFolder.
I have compile my apps and install it in : "C:\Program Files(x86)\CurrentFolder"
Peculiarities occur, when file "databaseFile.accdb" has been deleted from folder "CurrentFolder".
When I run "MyApps.exe", then login entry username and password, and then Entry ,read data. The Apps is still running.
This should not happen because "databaseFile.accdb" has been deleted.
Why it can happen? I am confused for this happen.
Anyone can explain this ? why my Apss still can access/read database.accdb
eventough the database was deleted.
Thanks in advance.
--Addition Information --
Before, i share folder "C:\Program Files(x86)\CurrentFolder" to network. and add Permissions to Everyone Full Control.
I hope this information can help our problem analysis.
Here source code my connection.cs
public Connection()
{
try
{
alamat = "Provider=Microsoft.ace.Oledb.12.0; Data Source="+Application.StartupPath+"\\databaseFile.accdb";
koneksi = new OleDbConnection(alamat);
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
public static Connection GetInstance(){
if(Connection.connection == null){
Connection.connection = new Connection();
}
return Connection.connection;
}
//this is for check wether the file databaseFile.accdb is exist in that folder
public int cekDb(string locasi)
{
int a=0;
if (File.Exists(locasi))
{
a = 1;
}
return a;
}
public int CekLogin(string user,string pass)
{
koneksi.Close();
koneksi.Open();
perintah = new OleDbCommand("select * from [user] where username = '" + user + "' and password = '" + pass + "';", koneksi);
myReader = perintah.ExecuteReader();
int count = 0;
while (myReader.Read())
{
leveluser = myReader["type"].ToString();
count++;
}
koneksi.Close();
return count;
}
In my login.cs
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text == "" || textBox2.Text == "")
{
MessageBox.Show("Please Fill your Username or Password");
textBox1.Focus();
}
else
{
if(connection.cekDb(Application.StartupPath+"\\databaseFile.accdb")==1){
int cek = connection.CekLogin(textBox1.Text.Trim().Replace("'", "''"), textBox2.Text.Trim().Replace("'", "''"));
if (cek != 0)
{
DashBoard entry = new DashBoard();
entry.Show();
UseWaitCursor = false;
}
else if (cek == 0)
{
// konek.Disconnect();
MessageBox.Show("Please Check your username and password !!");
}
else
{
MessageBox.Show(cek.ToString());
}
}
else
{
MessageBox.Show("File DatabaseFile.accdb Not Found !!");
}
}
}

MessageBox showing unwanted result

I'm new at this world of developing a software. So this may sound silly.
I'm working on developing a simple Login System at college, and I want to speed things up a little bit, my professor can be a tad, disorganized and it jeopardize the little time we have to learn a million things about programming.
I could get the program running and only opening the Main Form if the username and password are valid.
Before I researched and made a register button that will write data in my database, the message box was working properly.
But now, I cannot seem to make the message box show up saying if it is either, a successful login or if it is not.
My code is as following for the Login button:
private void VLogin_Click(object sender, EventArgs e)
{
try
{
string ConnectionString = "User ID=*****;Password=*******;" +
"Database=C:\\Users\\marqu_000\\Documents\\WindowsFormsApplication13\\Sistema.GDB;" +
"DataSource=localhost";
FbConnection addDetailsConnection = new FbConnection(ConnectionString);
addDetailsConnection.Open();
string SQLCommandText = "select * from LOGIN where USERNAME=#username and PASSWORD=#password";
FbCommand addDetailsCommand = new FbCommand(SQLCommandText, addDetailsConnection);
addDetailsCommand.Parameters.Add("#username", FbDbType.VarChar, 15).Value = userName.Text;
addDetailsCommand.Parameters.Add("#password", FbDbType.VarChar, 15).Value = userPassword.Text;
FbDataReader reader = addDetailsCommand.ExecuteReader();
while (reader.Read())
{
this.Visible = false;
MainWin MWin = new MainWin();
MWin.ShowDialog();
Application.Exit();
}
MessageBox.Show("Login Successful");
}
catch (Exception x)
{
MessageBox.Show("Invalid username or password");
MessageBox.Show(x.Message);
}
}
And this is my code for the register button:
private void registerUser_Click(object sender, EventArgs e)
{
try
{
string ConnectionString = "User ID=****;Password=****;" +
"Database=C:\\Users\\marqu_000\\Documents\\WindowsFormsApplication13\\Sistema.GDB;" +
"DataSource=localhost";
FbConnection addDetailsConnection = new FbConnection(ConnectionString);
addDetailsConnection.Open();
FbCommand SQLCommandTextInsert = new FbCommand("INSERT INTO LOGIN(USERNAME, PASSWORD, LEVEL) VALUES (#username,#password,#level)", addDetailsConnection);
SQLCommandTextInsert.Parameters.AddWithValue("username", registerUsername.Text);
SQLCommandTextInsert.Parameters.AddWithValue("password", registerPassword.Text);
SQLCommandTextInsert.Parameters.AddWithValue("level", registerLevel.Text);
SQLCommandTextInsert.ExecuteNonQuery();
MessageBox.Show("Registration completed!");
}
catch (FbException fbex)
{
//throw fbex;
MessageBox.Show("Invalid information, please verify!");
MessageBox.Show(fbex.Message);
}
}
If there is any good-for-nothing lines in there, and easiest ways to make those things, I would like to know.
I thank you all in advance for the help.
Marco.

ShowDialog is a blocking call, that means no code will run until that call completes. Which in this case is when your MWin closes. You'll need to display the success message before calling ShowDialog or call it from MWin.
Your Login failed message will only show when an exception occurs. I think if i read your code correctly if the reader returns no results (failed login) then you'll display "Login Succesful" and then doing nothing else.
You can use an if to determine if the database returned results and login failed is your else condition.

I finally made it!
I searched how to validate with a IF and could do it. This is how my code is now:
try
{
string ConnectionString = "User ID=*****;Password=*******;" +
"Database=C:\\Users\\marqu_000\\Documents\\WindowsFormsApplication13\\Sistema.GDB;" +
"DataSource=localhost";
FbConnection addDetailsConnection = new FbConnection(ConnectionString);
addDetailsConnection.Open();
string SQLCommandText = "select * from LOGIN where USERNAME=#username and PASSWORD=#password";
FbCommand addDetailsCommand = new FbCommand(SQLCommandText, addDetailsConnection);
addDetailsCommand.Parameters.Add("#username", FbDbType.VarChar, 15).Value = userName.Text;
addDetailsCommand.Parameters.Add("#password", FbDbType.VarChar, 15).Value = userPassword.Text;
FbDataReader reader = addDetailsCommand.ExecuteReader();
if (reader.Read())
{
this.Visible = false;
MessageBox.Show("Login Successful!");
MainWin MWin = new MainWin();
MWin.ShowDialog();
}
else
{
MessageBox.Show("Invalid username or password!");
}

asp.net authentication and authorisation

I am using Form authentication. Here I am using a login control and in (login.cs) control I am calling the following method to validate the user. Here I am using local name for both username and password and now I want to connect to the database so I can retrieve username and password.
private bool Authenticateme(string username, string password, bool remberusername)
{
String localusername = "username";
String localpassword = "amar";
if (username.Equals(localusername) && password.Equals(localpassword))
{
return true;
}
else
{
return false;
}
}

You could use the MemberShip and Role Providers

You need to implement OnAuthenticate by adding it like this:
<asp:Login OnAuthenticate="AuthenticateEventHandler" />
Add event handler in .cs file like this
private void OnAuthenticate(object sender, AuthenticateEventArgs e)
{
bool Authenticated = false;
Authenticated = SiteSpecificAuthenticationMethod(Login1.UserName, Login1.Password);
e.Authenticated = Authenticated;
}
implement SiteSpecificAuthenticationMethod that will validate user against database.
Here are the reference links:
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.login.authenticate.aspx
http://forums.asp.net/t/1403132.aspx
Let me know if you need more help.

Try the following and create a SQL Server database with field username and password
SQlConnection con = new SqlConnection("Database connection string");
const string uName="UserName";
const string pWord="Password";
public bool getAuthenticate(string UserName,string Password)
{
con.Open();
SqlCommand cmd = new SqlCommand(con);
SQlParameter[] param=new SqlParameter[]{
new SqlParamter(uName,UserName),
new SqlParameter(pWord,Password)
};
cmd.Parameters.AddRanage(param);
SqlDataReader rd;
rd = cmd.executeReader();
if(rd.read())
{
con.Close();
return true;
}
else
{
con.Close();
return false;
}
}

In winform button needs to be clicked twice for firing event

I have a buttton on the click event of which I am calling a function.I have set the accept button property to that button.But it is not firing the event on single click.
private void btnConnect_Click(object sender, EventArgs e)
{
try
{
//Function call for validating the textboxes entry
ValidateForm();
if(lblMessage.Text != string.Empty)
{
//Function call for binding the dropdown with all DB names
BindDBDropDown();
//Function call for binding the operation names in dropdown
SetOperationDropDown();
}
else
{
//Else give the error message to user
lblMessage.Text = "Invalid Credentials";
}
}
catch(Exception ex)
{
//All the exceptions are handled and written in the EventLog.
EventLog log = new EventLog("Application");
log.Source = "MFDBAnalyser";
log.WriteEntry(ex.Message);
}
}
public void BindDBDropDown()
{
SqlConnectionStringBuilder objConnectionString = new SqlConnectionStringBuilder();
objConnectionString.DataSource = txtHost.Text;
objConnectionString.UserID = txtUsername.Text;
objConnectionString.Password = txtPassword.Text;
SqlConnection sConnection = new SqlConnection(objConnectionString.ConnectionString);
//If connected then give this message to user
lblMessage.Visible = true;
lblMessage.Text = "You are connected to the SQL Server....";
try
{
//To Open the connection.
sConnection.Open();
//Query to select the list of databases.
string selectDatabaseNames = #"SELECT
NAME
FROM
[MASTER]..[SYSDATABASES]";
//Create the command object
SqlCommand sCommand = new SqlCommand(selectDatabaseNames, sConnection);
//Create the data set
DataSet sDataset = new DataSet("master..sysdatabases");
//Create the dataadapter object
SqlDataAdapter sDataAdapter = new SqlDataAdapter(selectDatabaseNames, sConnection);
sDataAdapter.TableMappings.Add("Table", "master..sysdatabases");
//Fill the dataset
sDataAdapter.Fill(sDataset);
//Bind the database names in combobox
DataViewManager dsv = sDataset.DefaultViewManager;
//Provides the master mapping between the sourcr table and system.data.datatable
cmbDatabases.DataSource = sDataset.Tables["master..sysdatabases"];
cmbDatabases.DisplayMember = "NAME";
cmbDatabases.ValueMember = ("NAME");
}
catch(Exception ex)
{
//All the exceptions are handled and written in the EventLog.
EventLog logException = new EventLog("Application");
logException.Source = "MFDBAnalyser";
logException.WriteEntry(ex.Message);
MessageBox.Show ("Login Failed!!", "Error Occured");
}
finally
{
//If connection is not closed then close the connection
if(sConnection.State != ConnectionState.Closed)
{
sConnection.Close();
}
}
}
Can anybody help me out??

Uh, on the first click, does lblMessage contain any text?
Because if not, the first time you run it, it will fail the conditional test and insert the string "Invalid Credentials" into the label. Then, the second time you run it, it will pass the conditional test and call the BindDBDropDown method as you're expecting.
Specifically, this section of your code:
if(lblMessage.Text != string.Empty)
{
//Function call for binding the dropdown with all DB names
BindDBDropDown();
//Function call for binding the operation names in dropdown
SetOperationDropDown();
}
else
{
//Else give the error message to user
lblMessage.Text = "Invalid Credentials";
}
I assume that you're either trying to check that the contents of a textbox where the user has entered their credentials are not empty, or that you want to make sure an error message is not currently displayed in lblMessage. Make sure that your code accurately reflects your intentions!