Update UI from dynamic created class

Question

I am dynamic creating several classes and labels. I want to update the label text from my class, but I don't have any idea how to implement it.

My class:

  public partial class ScannerUtility : INotifyPropertyChanged
{
    public System.Timers.Timer timerHeartBeat = new System.Timers.Timer();
    public DateTime lastHeartBeat = new DateTime();
    public string heartBeatMessage = string.Empty;
    public event PropertyChangedEventHandler PropertyChanged;


    private void NotifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    public void EnableScannerUtility()
    {
        timerHeartBeat = new System.Timers.Timer();
        timerHeartBeat.AutoReset = true;
        timerHeartBeat.Interval = 5000;// 35000;
        timerHeartBeat.Elapsed += TimerHeartBeat_Elapsed;
        timerHeartBeat.Start();
    }

    private void TimerHeartBeat_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
    {
        TimeSpan timeSinceLastHeartbeat = DateTime.Now.ToUniversalTime() - lastHeartBeat;
        if (timeSinceLastHeartbeat > TimeSpan.FromSeconds(30))
        {
            HeartBeatMessage = "No Answer from Scanner";
        }
        else
        {
            HeartBeatMessage = "Scanner OK";
        }
    }

    public string HeartBeatMessage
    {
        get { return this.heartBeatMessage; }

        set
        {
            if (value != this.heartBeatMessage)
            {
                this.heartBeatMessage = value;
                NotifyPropertyChanged("heartBeatMessage");
            }
        }
    }


}

And the loop where I created it from the main form:

 private void CreateSckanners()
    {
       foreach (BarCodeNodes item in iBarcodeScanners)
        {
            ScannerUtility util = new ScannerUtility();
            util.EnableScannerUtility();

            Label lbl = new Label();
            lbl.Text = item.IP.ToString();
            lbl.Name = item.IP.ToString();
            lbl.DataBindings.Add("Text", util, "HeartBeatMessage", false, DataSourceUpdateMode.OnPropertyChanged);
            flowLayoutPanel1.Controls.Add(lbl);
            flowLayoutPanel1.Update();
        }
    }

I want the Label to be updated when the timer is elapsed.

score 1 · Accepted Answer · edited May 23 '17 at 12:28

1

I'm affraid that you can not use DataBindigns in your situation. You have to stick whith the InvokeRequired style. Here, SO question about updating controls in another thread.

edited May 23 '17 at 12:28

Community

1
1

answered Mar 18 '15 at 11:51

jlvaquero

8,571
1
29
45

1

He __can__ through the proper use of `SynchronizationContext`. However, I would always rather just avoid my back-end classes firing events from another threads - there's very few situations where you really must do that. – bokibeg Mar 18 '15 at 12:02

jlvaquero · Answer 2 · 2015-03-24T08:26:47.190

bokibeg is right. I put the code in case someone is interested.

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.Threading;

namespace WindowsFormsApplication1
{
 public partial class Form1 : Form
 {
  public Form1()
  {
   InitializeComponent();
   this.Load += new EventHandler(Form1_Load);
  }

  void Form1_Load(object sender, EventArgs e)
  {
   ScannerUtility util = new ScannerUtility(SynchronizationContext.Current);
   util.EnableScannerUtility();
   util.HeartBeatMessage = "Waiting for scanner...";

   this.SuspendLayout();
   Label lbl = new Label();
   lbl.Text = "Waiting for scanner...";
   lbl.Name = "lblTimer";
   lbl.Location = new System.Drawing.Point(15, 15);
   lbl.AutoSize = true;
   lbl.DataBindings.Add("Text", util, "HeartBeatMessage", false, DataSourceUpdateMode.OnPropertyChanged);
   this.Controls.Add(lbl);
   this.ResumeLayout(true);
  }
 }

 public partial class ScannerUtility : INotifyPropertyChanged
 {
  private SynchronizationContext _uiThreadContext;
  public System.Timers.Timer timerHeartBeat = new System.Timers.Timer();
  public DateTime lastHeartBeat = new DateTime();
  public string heartBeatMessage = string.Empty;
  public event PropertyChangedEventHandler PropertyChanged;

  public ScannerUtility(SynchronizationContext uiThreadContext)
  {
   _uiThreadContext = uiThreadContext;
  }

  private void NotifyPropertyChanged(String info)
  {
   if (PropertyChanged != null)
   {
    _uiThreadContext.Post(onUIPropertyChanged, new PropertyChangedEventArgs(info));
   }
   ;
  }

  private void onUIPropertyChanged(object state)
  {
    PropertyChanged(this, (PropertyChangedEventArgs)state);
  }

  public void EnableScannerUtility()
  {
   timerHeartBeat = new System.Timers.Timer();
   timerHeartBeat.AutoReset = true;
   timerHeartBeat.Interval = 5000;// 35000;
   timerHeartBeat.Elapsed += TimerHeartBeat_Elapsed;
   timerHeartBeat.Start();
  }

  private void TimerHeartBeat_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
  {
   TimeSpan timeSinceLastHeartbeat = DateTime.Now.ToUniversalTime() - lastHeartBeat;
   if (timeSinceLastHeartbeat > TimeSpan.FromSeconds(30))
   {
    HeartBeatMessage = "No Answer from Scanner";
   }
   else
   {
    HeartBeatMessage = "Scanner OK";
   }
  }

  public string HeartBeatMessage
  {
   get
   {
    return this.heartBeatMessage;
   }

   set
   {
    if (value != this.heartBeatMessage)
    {
     this.heartBeatMessage = value;
     NotifyPropertyChanged("HeartBeatMessage");
    }
   }
  }
 }
}

Update UI from dynamic created class

2 Answers2