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Logic issue on reading ALL data from the from the listbox that is coming from thread in c#

I am modifying to first question attempt.
I need help passing the data from a listbox and pass it to another method so every time the listbox gets data add it from the tread, it should also send that data to my new method and it to the my list because in that method I will be doing some parsing because the data from the listbox is a long string barcode but I don't need help on parsing the data because I can do that, the part I need help only is to pass the data from thread that is passing it to the listbox it should also be send to my method ReadAllData() so in that method I will received the data and then I will do the parsing the make a return.
Here is the method where the listbox is stored and receives the data from a thread from telnet port 23
Here is the code I need to send the data from the lst_BarcodeScan to the method ReadAllData method and store to my list.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Sockets;
using System.Runtime.Remoting.Messaging;
using System.Security.Authentication.ExtendedProtection;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace BarcodeReceivingApp
{
public class TelnetConnection
{
private Thread _readWriteThread;
private TcpClient _client;
private NetworkStream _networkStream;
private string _hostname;
private int _port;
private BarcodeReceivingForm _form;
private bool _isExiting = false;
public TelnetConnection(string hostname, int port)
{
this._hostname = hostname;
this._port = port;
}
public TelnetConnection()
{
}
public void ServerSocket(string ip, int port, BarcodeReceivingForm f)
{
this._form = f;
try
{
_client = new TcpClient(ip, port);
}
catch (SocketException)
{
MessageBox.Show(#"Failed to connect to server");
return;
}
_networkStream = _client.GetStream();
_readWriteThread = new Thread(ReadWrite);
//_readWriteThread = new Thread(() => ReadWrite(f));
_readWriteThread.Start();
}
public void Exit()
{
_isExiting = true;
}
public void ReadWrite()
{
var received = "";
do
{
received = Read();
if (received == null)
break;
if (_form.lst_BarcodeScan.InvokeRequired)
{
_form.lst_BarcodeScan.Invoke(new MethodInvoker(delegate
{
_form.lst_BarcodeScan.Items.Add(received + Environment.NewLine);
}));
}
} while (!_isExiting);
CloseConnection();
}
public List<string> ReadAllData()
{
var obtainData = new List<string>();
return obtainData;
}
public string Read()
{
var data = new byte[1024];
var received = "";
var size = _networkStream.Read(data, 0, data.Length);
if (size == 0)
return null;
received = Encoding.ASCII.GetString(data, 0, size);
return received;
}
public void CloseConnection()
{
MessageBox.Show(#"Closed Connection",#"Important Message");
_networkStream.Close();
_client.Close();
}
}
}
Main class that will call the methods from the telnetconnection class or any other classes I will add.
using System;
using System.Windows.Forms;
namespace BarcodeReceivingApp
{
public partial class BarcodeReceivingForm : Form
{
//GLOBAL VARIABLES
private const string Hostname = "myip";
private const int Port = 23;
private TelnetConnection _connection;
public BarcodeReceivingForm()
{
InitializeComponent();
//FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
WindowState = FormWindowState.Maximized;
}
private void btn_ConnectT_Click(object sender, EventArgs e)
{
_connection = new TelnetConnection(Hostname, Port);
_connection.ServerSocket(Hostname, Port, this);
}
private void btn_StopConnection_Click(object sender, EventArgs e)
{
//_connection = new TelnetConnection(Hostname, Port);
//_connection.ServerSocket(Hostname, Port, this);
_connection.Exit();
}
private void btn_RemoveItemFromListAt_Click(object sender, EventArgs e)
{
for (var i = lst_BarcodeScan.SelectedIndices.Count - 1; i >= 0; i--)
{
lst_BarcodeScan.Items.RemoveAt(lst_BarcodeScan.SelectedIndices[i]);
}
}
private void BarcodeReceivingForm_Load(object sender, EventArgs e)
{
lst_BarcodeScan.SelectionMode = SelectionMode.MultiSimple;
}
private void btn_ApplicationSettings_Click(object sender, EventArgs e)
{
var bcSettingsForm = new BarcodeReceivingSettingsForm();
bcSettingsForm.Show();
}
private void btn_ClearBarcodeList_Click(object sender, EventArgs e)
{
lst_BarcodeScan.Items.Clear();
}
}
}

The easiest way to implement without adding more complexity to the thread is to simply raise an event on the listbox when and item is added to it. The problem is that the listbox do no have any events that allow to do that but you can create your own version with a dozen lines of code.
The goal is to create a derived control of the listbox then you add to it a method to trigger a custom event when an item is added and bingo.
Here's the custom listbox class with the custom EventArgs.
// custom override class over the list box so we can create an event when items are added
public class ListBoxWithEvents : ListBox
{
// the event you need to bind to know when items are added
public event EventHandler<ListBoxItemEventArgs> ItemAdded;
// method to call to add items instead of lst.Items.Add(x);
public void AddItem(object data)
{
// add the item normally to the internal list
var index = Items.Add(data);
// invoke the event to notify the binded handlers
InvokeItemAdded(index);
}
public void InvokeItemAdded(int index)
{
// invoke the event if binded anywhere
ItemAdded?.Invoke(this, new ListBoxItemEventArgs(index));
}
}
// basic event handler that will hold the index of the item added
public class ListBoxItemEventArgs : EventArgs
{
public int Index { get; set; } = -1;
public ListBoxItemEventArgs(int index)
{
Index = index;
}
}
Now you need to change your listbox on your form with the ListBoxWithEvents instead. You have 2 ways to do this but i'll give you the easiest. Compile your code and go in the design window for the form. In your toolbox you should have the ListBoxWithEvents control now and you can simply drag and drop in your form and replace the one you have. Since it derive from the listbox all it has is extra features. It didn't lose anything it had before.
Now you need to change 2 things. In your form select the new ListBoxWithEvents control and go in the properties events and you will find the new event called ItemAdded you can double click that and it should create an event like the following. I have also thrown in a sample MessageBox that display all you will need.
private void ListBox1_ItemAdded(object sender, ListBoxItemEventArgs e)
{
MessageBox.Show("Item was added at index " + e.Index + " and the value is " + listBox1.Items[e.Index].ToString());
}
Finally in order to trigger that event you need to use the new method lst.AddItem(object); instead of lst.Items.Add(object); so according to your sample code you need to change this :
_form.lst_BarcodeScan.Invoke(new MethodInvoker(delegate
{
_form.lst_BarcodeScan.Items.Add(received + Environment.NewLine);
}));
to this :
_form.lst_BarcodeScan.Invoke(new MethodInvoker(delegate
{
_form.lst_BarcodeScan.AddItem(received + Environment.NewLine);
}));
Try it and now you should have that event fire every time something is added to the list.
Since you are pretty new to programming i find it important to mention that this event will trigger on the UI thread and not the thread you created. This mean it behave normally like clicking on a button triggers a button_click(object sender, EventArgs e) event. No special thread involved whatsoever.

Implementing async/task/await in a multi-tier windows form application

I would appreciate some help with async/Task implementation in my Windows Form application.
In this app, I retrieve data from the datacenter SQl server database using WCF services, so part of this code runs on the client and some on the datacenter server where it retrieves the data and returns it. I’d like to optimize the code using async/Task on the clien or server or preferably both. The example code starts with a Windows Form with a button, when the button is clicked it gets a value from the database, displays it and updates a local variable.
I’m not clear if I can simply implement async/Task and Task.Run in the first button click event or whether the code should be cascaded through all methods, or something in between. I'm also not clear on how to handle the wcf service.
I’ve created a simplified example of the code, pretty close to sequentially.
In this code, the return value updates the windows form. I’d like to see how this code is optimized using async/Task await for this purpose and what would be different if the code did not return a value.
public partial class Form1 : Form
{
int returnvalue = 0;
public Form1()
{
InitializeComponent();
}
private void btnGetResult_Click(object sender, EventArgs e)
{
int rowcount = ChangeProductPrice(.05m);
txtResult.Text = rowcount.ToString();
}
private int ChangeProductPrice(decimal priceincrease)
{
int rv = MyData.WebServiceObject.ChangePrice(priceincrease);
UpdateLocalVariables(rv);
return rv;
}
private void UpdateLocalVariables(int rv)
{
returnvalue = rv;
}
}
public static class MyData
{
private static IMyDataWCFService _webserviceobject = null;
public static IMyDataWCFService WebServiceObject
{
get
{
if (_webserviceobject is null)
{
//...code to initialize it
}
return _webserviceobject;
}
}
}
[ServiceContract(SessionMode = SessionMode.Required)]
public interface IMyDataWCFService
{
[OperationContract]
int ChangePrice(decimal priceincrease);
}
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession, ConcurrencyMode = ConcurrencyMode.Multiple)]
public class MyDataWCFService : IMyDataWCFService
{
private MyDataService _serviceObject = null;
private MyDataService ServiceObject
{
get
{
if (_serviceObject == null)
{
_serviceObject = new MyDataService();
}
return _serviceObject;
}
}
public int ChangePrice(decimal priceincrease)
{
return ServiceObject.ChangePrice(priceincrease);
}
}
public class MyDataService //running on server
{
public int ChangePrice(decimal priceincrease)
{
int rows = 0;
SqlConnection conn = null;
try
{
conn = this.GetSqlConnection();
using (SqlCommand cmd = new SqlCommand())
{
cmd.CommandType = CommandType.StoredProcedure;
cmd.Connection = conn;
cmd.CommandText = "mysp_UpdatePrice";
cmd.Parameters.Add(new SqlParameter("#Rate", priceincrease));
conn.Open();
rows = cmd.ExecuteNonQuery();
}
}
catch (Exception ex)
{
ProcessError(ex);
}
finally
{
if (conn != null)
ReturnSqlConnection(conn);
}
return rows;
}
private SqlConnection GetSqlConnection()
{
//dostuff;
return new SqlConnection();
}
private void ProcessError(Exception ex)
{
//dostuff;
}
private void ReturnSqlConnection(SqlConnection conn)
{
//dostuff;
}
}

How to Check connection status at run time using C#.net (winforms)

I have client server application (Lan base). Initially the client application successfully connects to server but later at run time the connection is being lost due to some reason (e.g server machine shutdown ). This is triggering an error something like UNABLE TO CONNECT TO HOST. How can i check the status of connection at run time?
The code is as follows
Connection class
using MySql.Data.MySqlClient;
namespace Connection_Checker
{
public class Connection
{
public static MySqlConnection cnn = new MySqlConnection("Server=localhost;Database=arc;User Id=root;Password=root;");
}
}
Form
private void Form1_Load(object sender, EventArgs e)
{
Connection.cnn.Open();
}
//and timer
private void timer1_Tick(object sender, EventArgs e)
{
if (Connection.cnn.State == ConnectionState.Open)
{
this.Text = "Connected";
}
else
{
this.Text = "Disconnected";
return;
}
}
my timer is enable = true

If I were you in the form I would not open the connection in form load event.
Instead my method where I would be fetching the data would be something like this
using MySql.Data.MySqlClient;
namespace Connection_Checker
{
public class Connection
{
public static connectionString = "Server=localhost;Database=arc;User Id=root;Password=root;";
}
}
In the form
private void GetData()
{
try{
using (MySqlSqlConnection connection = new MySqlSqlConnection(Connection.connectionString ))
{
connection.Open();
//GetData
connection.Close();
}
}
catch
{
MessageBox.Show("An error occurred while trying to fetch Data");
}
}
private void Form1_Load(object sender, EventArgs e)
{
//I would avoid this.
// Connection.cnn.Open();
}
//I am not sure why you are having this.
private void timer1_Tick(object sender, EventArgs e)
{
//if (Connection.cnn.State == ConnectionState.Open)
//{
// this.Text = "Connected";
//}
//else
//{
// this.Text = "Disconnected";
// return;
//}
}

Catching transmit errors does not tell you when the connection fails. It only tells you that the connection was not available when you tried to use it.
For continuous presence-monitoring using a timer as per your example, use this extension method to directly query the TCP connection state.
public static class Extensions
{
/// <summary>
/// Obtain the current state of the socket underpinning a TcpClient.
/// Unlike TcpClient.Connected this is reliable and does not require
/// capture of an exception resulting from a failed socket write.
/// </summary>
/// <param name="tcpClient">TcpClient instance</param>
/// <returns>Current state of the TcpClient.Client socket</returns>
public static TcpState GetState(this TcpClient tcpClient)
{
var foo = IPGlobalProperties.GetIPGlobalProperties().GetActiveTcpConnections()
.SingleOrDefault(x => x.LocalEndPoint.Equals(tcpClient.Client.LocalEndPoint));
return foo != null ? foo.State : TcpState.Unknown;
}
}
However, as already mentioned by others in comments, your dependence on continuous connection probably reflects serious design flaws in your application. You should heed the advice you have been given and redesign your app. Hogging connections seriously limits scalability, and will not make you popular with your network administrator or your database administrator.

Disable certain buttons depending on which user has logged in

In login form, When I login as Jack which exist in the DOCTOR table, it will go to page_two. I want to disable nurse button 1, and nurse button 2 since Jack is not a nurse but a doctor. Then for the opposite, if I login as Mary, which exist in the NURSE table, it will go to page_two. I want to disable doctor button 1, and doctor button 2 since Mary is not a doctor but a nurse.
The button names for Page_two is btnDoctor1, btnDoctor2, btnNurse1 and btnNurse2
//login Form codes
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.SqlClient;
using System.Configuration;
namespace GRP_02_03_SACP
{
public partial class page_one : Form
{
public page_one()
{
InitializeComponent();
}
private void page_one_Load(object sender, EventArgs e)
{
}
private void btnLogin_Click(object sender, EventArgs e)
{
//retrieve connection information info from App.config
string strConnectionString = ConfigurationManager.ConnectionStrings["sacpConnection"].ConnectionString;
//STEP 1: Create connection
SqlConnection myConnect = new SqlConnection(strConnectionString);
//STEP 2: Create command
string strCommandtext = "SELECT dUsername, dPassword from DOCTOR";
// Add a WHERE Clause to SQL statement
strCommandtext += " WHERE dUsername=#dname AND dPassword=#dpwd;";
strCommandtext += "SELECT nUsername, nPassword from NURSE WHERE nUsername=#nname AND nPassword=#npwd;";
SqlCommand cmd = new SqlCommand(strCommandtext, myConnect);
cmd.Parameters.AddWithValue("#dname", textUsername.Text);
cmd.Parameters.AddWithValue("#dpwd", txtPassword.Text);
cmd.Parameters.AddWithValue("#nname", textUsername.Text);
cmd.Parameters.AddWithValue("#npwd", txtPassword.Text);
try
{
// STEP 3: open connection and retrieve data by calling ExecuteReader
myConnect.Open();
// STEP 4: Access Data
SqlDataReader reader = cmd.ExecuteReader();
while (reader.Read()) //For Doctor
{
if (MessageBox.Show("Login Successful") == DialogResult.OK)
{
page_two form = new page_two();
form.Show();
return;
}
}
reader.NextResult();
while (reader.Read()) //For Nurse
{
if (MessageBox.Show("Login Successful") == DialogResult.OK)
{
page_two form = new page_two();
form.Show();
return;
}
}
//STEP 5: close connection
reader.Close();
MessageBox.Show("Invalid username or password");
}
catch (SqlException ex)
{
}
finally
{
//STEP 5: close connection
myConnect.Close();
}
}
}
}

I suggest you to create some Person class to hold person data:
public class Person
{
public string Name { get; set; }
public JobPosition Position { get; set; }
// etc
}
Where Position is a enum for job positions available for your persons:
public enum JobPosition
{
Doctor,
Nurse
}
Next step will be separating data access logic from presentation code by moving database queries to some repository class:
public class PersonRepository
{
public Person GetPerson(string userName, string password)
{
// execute query and create Person instance
}
}
Also I'd create separate login form which should be shown before your main form starts. It should use PersonRepository to get Person instance which should be passed to MainForm constructor:
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
LoginForm loginForm = new LoginForm();
if (loginForm.ShowDialog() != DialogResult.OK)
return;
Application.Run(new MainForm(loginForm.Person));
On main form use position of logged in person to enable or disable controls:
public partial class MainForm : Form
{
private Person _person;
public MainForm(Person person)
{
InitializeComponent();
_person = person;
}
private void MainForm_Load(object sender, EventArgs e)
{
fooButton.Enabled = (_person.Position == JobPosition.Doctor);
// etc
}
}

Access TextBox from Static method in C#?

I have 2 classes: MyForm and Database
In MyForm I have a method to change a label text to show error:
public void printError(string text){
label1.Text = text;
}
My Database class needs to access that method too, so I make it static:
public static void printError(MyForm form, string text){
form.label1.Text = text;
}
Now the problem is, how do I call that method from Database class?
This question I found said that I need to pass MyForm into Database's contructor like this:
class MyForm : Form{
Database db;
public Form(){
db = new Database(this);
}
}
class Database{
MyForm form;
public Database(MyForm f){
form = f;
}
...
//then I can access the printError like this
MyForm.printError(form, "You got error");
}
I tried that and it freezes the form. Any other solution?
Thanks

Here is a very simple example of how you can achieve this without your data layer knowing about your UI:
class MyForm : Form
{
Database db;
public Form()
{
db = new Database(this);
}
public void DoSomething()
{
var errors = db.Login("", "");
if (errors.Any())
label1.Text = errors.First(); // Or you can display all all of them
}
}
class Database
{
public List<string> Login(string username, string password)
{
var errors = new List<string>();
if (string.IsNullOrEmpty(username))
errors.Add("Username is required");
if (string.IsNullOrEmpty(password))
errors.Add("Password is required");
[...]
return errors;
}
}

Like #Matthew Ferreira and others have stated the design is not idea, but here's something to get you started.
class MyForm : Form
{
public void SomeMethod()
{
var dataAccess = new Repository();
dataAccess.ExecuteQuery();
if (dataAccess.Exceptions.Any())
{
// display your error messages
form.label1.Text = dataAccess.Exceptions.Select(x => x.ToString());
}
}
}
class Repository
{
private readonly HashSet<Exception> _exceptions = new HashSet<Exception>();
public IEnumerable<Exception> Exceptions
{
get { return _exceptions; }
}
public int ExecuteQuery()
{
var numberOfRecordsAffected = 0;
try
{
// do something
}
catch (Exception ex)
{
// normall catching exceptions is a bad idea
// and you should really catch the exception at the
// layer best equiped to deal with it
_exceptions.Add(ex);
}
// but, for the purpose of this example we might want to add some logic to try the query on another database ????
try
{
// do something
}
catch (Exception ex)
{
_exceptions.Add(ex);
}
return numberOfRecordsAffected;
}
}

You need to look up "seperation of concerns". Its really bad to mix your UI code with you Database Access Layer (DAL). Better to bind the UI to business objects that are populated via a DAL.
To let the UI know about an error you could simply use a delegate.
namespace OperationErrorDelegate
{
public delegate void OperationErrorHandler(Exception ex);
public class DAL
{
public event OperationErrorHandler ReportError;
public void DoDALOperationThatCausesError()
{
try
{
int i = 1;
int j = 0;
int k = i/j;
}
catch (Exception ex)
{
ReportError(ex);
}
}
}
}
Add this code to the form:
using System ;
using System.Windows.Forms;
namespace OperationErrorDelegate
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
DAL DAL = new DAL();
DAL.ReportError += new OperationErrorHandler(DAL_OperationErrorProgress);
DAL.DoDALOperationThatCausesError();
}
private void DAL_OperationErrorProgress(Exception ex)
{
label1.Text = ex.Message;
}
}
}

Assuming the OP's requirement is to display an error message in a label, when the credentials are wrong:
private void btn_login_Click(object sender, EventArgs e)
{
MySqlConnection con = new MySqlConnection("server=localhost;uid=root;password=abc;database=mydb");
MySqlCommand cmd = new MySqlCommand("select * from emp where name='" + textBox1.Text + "'and pwd='" + textBox2.Text + "'",con);
con.Open();
MySqlDataReader dr = cmd.ExecuteReader();
if (dr.Read())
{ //successful
//navigate to next page or whatever you want
}
else
Label1.Text("Invalid userid or password");
con.Close();
}
And if you need error message for wrong data type (the user input string but the database column is Integer), then use validations at client side. You dont need to do it at backend, since that will be a burden.
You can use regular expressions for that in the button_click itself.