C# update label from another class

Question

How can i update label from another class, i have seen many answer, but not function for my example. here is my code:

class Form1: look like this:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace login
{
public partial class Form1 : Form
{

    public static Form1 Instance { get; private set; }


    public Form1()
    {
        InitializeComponent();
        Instance = this;
        MediaEvent device = new MediaEvent();

    }




    private void button2_Click(object sender, EventArgs e)
    {            
        MediaEvent msg = new MediaEvent();
        string u = textBox1.Text;
        string p = textBox2.Text;

        msg.checkLogin(u, p);
        label2.Text = msg.getMessage();

    }

    public void TextStatus(string aString)
    {
        // Place messages in Main Display list box window

        this.lstatus.Text = aString;
    }
    public void TextToBox(string aString)
    {
        // Place messages in Main Display list box window

        this.listBox1.Items.Insert(0, aString);
    }

    public void listBox1_SelectedIndexChanged(object sender, EventArgs e)
    {

    }
}
}

Class MediaEvent look like this:

using System;
using System.Collections.Generic;
using System.Text;
using System.Management;
using System.Windows.Forms;

namespace login
{
class MediaEvent: IDisposable
{
    public string MyMsg { get; set; }
    public string State { get; set; }
    public string getMessage()
        {
            return MyMsg;
        }
    public void checkLogin(string u, string p)
    {
        if((u != "user") && (p != "password"))
        {
            MyMsg +="Id or password no correct, please try again.";
        }
    }
    Form1 MainForm;



    private ManagementEventWatcher watcherAttach;
    private ManagementEventWatcher watcherRemove;

    public MediaEvent()
    {
        if (watcherAttach == null)
        {
            watcherAttach = new ManagementEventWatcher();          
            watcherAttach.Query = new WqlEventQuery("SELECT * FROM Win32_DeviceChangeEvent WHERE EventType = 2");
            watcherAttach.EventArrived += new EventArrivedEventHandler(watcher_EventArrived);
            //Form1.Instance.TextStatus("On");
            watcherAttach.Start();
        }

        if (watcherRemove == null)
        {
            watcherRemove = new ManagementEventWatcher();            
            watcherRemove.Query = new WqlEventQuery("SELECT * FROM Win32_DeviceChangeEvent WHERE EventType = 3");
            watcherRemove.EventArrived += new EventArrivedEventHandler(watcher_EventRemoved);
            //Form1.Instance.TextStatus("Off");
            watcherRemove.Start();
        }
    }

    /// <summary>
    /// Used to dispose of the USB device watchers when the USBControl class is disposed of.
    /// </summary>
    public void Dispose()
    {
        if (watcherAttach != null)
        {
            watcherAttach.Stop();
            watcherAttach.Dispose();                
            watcherAttach = null;
        }

        if(watcherRemove != null)
        {
            watcherRemove.Stop();
            watcherRemove.Dispose();
            watcherRemove = null;                
        }

    }



    void watcher_EventArrived(object sender, EventArrivedEventArgs e)
    {
        Form1.Instance.TextStatus("On");
        //MessageBox.Show("On");
    }

    void watcher_EventRemoved(object sender, EventArrivedEventArgs e)
    {
        Form1.Instance.TextStatus("Off");
        //MessageBox.Show("off");
    }




    ~MediaEvent()
    {
        this.Dispose();
    }

}

}

This is the full code more clearly. i need your help

Answer 1

You can reference the Form by setting up a method on the Form_Load.

private void Form1_Load(object sender, EventArgs e)
{
    MyClass.SetUIComponents(this);
}

After that you create a global variable in your class and initialize your variable with the form.

public class MyClass{
  //Constructor
  public MyClass(){...}

  public void SetUIComponents(Form1 Form1)
  {
      // Get MainForm to reference public UI objects 
      this.Form = Form;
  }
}

After you have initialized Form1 global variable, you can reference the Form. Remember that objects such as lables or buttons must have their modifiers (Found in objects Properties Form1[Design]) changed to public so you can change the text, name, etc...

Answer 2

you need to change your code to something like the following

public partial class Form1 : Form
    {
        private static Form1 _instance; 
        public Form1()
        {

            InitializeComponent();
            _instance = this; 
        }


        public string TextStatus
        {
            get { return StatusLabel.Text;  }
            set { StatusLabel.Text = value;  }

        }

        public static Form1 Instance { get { return  _instance;  }}



    }

void watcher_EventArrived(object sender, EventArrivedEventArgs e)
    {
        Form1.Instance.TextStatus ="On"; // nothing is changed in label
        //MessageBox.Show("On");
    }