Do I use a thread to update a label from a class?

[mojo69]

I have a form with a label and a progressbar. I would like to use these to update the user with the progress made on moving some images. Do I use a thread to start the image processing?

[jmcilhinney]

You would use a secondary thread to perform the processing but then you must update the UI on the UI thread. The easiest option would be to use a BackgroundWorker. Follow the CodeBank link in my signature and check out my thread on Using The BackgroundWorker for information and examples.

[mojo69]

Thanks. I was looking at BackgroundWorker earlier. It is used in conjunction with a eventhandler, correct?

[jmcilhinney]

It is used in exactly the way it is demonstrated in my examples that I provided a link for in my previous post.

[mojo69]

OK I am using the following code in a form to move files. The codebank submission helped get that working at least. Thanks to jmcilhinney. However I think that I want a separate class to house the file moving process. Going from what I have so far how can I keep updating the label from this new class? Seems like it should not be hard to do but I am not connecting the dots for whatever reason.
Thanks.

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.IO;

namespace VisualScrapUtil
{
    public partial class frmUtil : Form
    {
        public frmUtil()
        {
            InitializeComponent();
            bgWorker.WorkerReportsProgress = true;
            bgWorker.WorkerSupportsCancellation = true;
        }

        private void btnPath_Click(object sender, EventArgs e)
        {
            FolderBrowserDialog fbd = new FolderBrowserDialog();
            fbd.Description = "Select Images Folder";
            if (fbd.ShowDialog() == DialogResult.OK)
            {
                txtFolder.Text = fbd.SelectedPath;
                txtDestination.Text = txtFolder.Text;
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (txtFolder.TextLength != 0 || txtDestination.TextLength != 0)
            {
                if (bgWorker.IsBusy != true)
                {
                    label1.Text = DateTime.Now.ToString();
                    bgWorker.RunWorkerAsync();
                }
            }
            else
            {
                label2.Text = "PICK FILES";
            }
        }

        private void btnDest_Click(object sender, EventArgs e)
        {
            FolderBrowserDialog fbd = new FolderBrowserDialog();
            fbd.Description = "Select Images Destination";
            if (fbd.ShowDialog() == DialogResult.OK)
            {
                txtDestination.Text = fbd.SelectedPath;
            }
        }

        private void btnCancelMove_Click(object sender, EventArgs e)
        {
            bgWorker.CancelAsync();
        }

        private void bgWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            //BackgroundWorker worker = new BackgroundWorker();
            //if (worker.CancellationPending == true)
            if (bgWorker.CancellationPending == true)
            {
                e.Cancel = true;
            }
            else
            {
                ProcessImages(txtFolder.Text, txtDestination.Text);   
            }
        }

        private void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            label2.Text = (e.ProgressPercentage.ToString() + "%");
        }

        private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled == true)
            {
                label2.Text = "CANCELLED";
            }
            else if (e.Error !=null)
            {
                label2.Text = "Error: " + e.Error.Message;
            }
            else
            {
                label4.Text = DateTime.Now.ToString();
                label2.Text= "FINISHED";
            }
        }
        public int ProcessImages(String SourceFolder, String DestinationFile)
        {
            //leave the fingerprint records alone for now
            //only process the .jpg files
            try
            {
                string[] fileImages = Directory.GetFiles(SourceFolder);
                Double dblNumFiles = fileImages.Length;
                
                Int32 intPercentDone = 0;
                Double dblRecCnt = 0;
                foreach (string fileImage in fileImages)
                {
                    dblRecCnt = ++dblRecCnt;
                    intPercentDone = (int)(((float)dblRecCnt / (float)dblNumFiles) * 100);
                    
                    bgWorker.ReportProgress(intPercentDone);
                    if (fileImage.Contains(".jpg"))
                    {
                        string[] paths = fileImage.Split('\\');
                        string newImage = paths[paths.Length - 1];
                        if (newImage.Substring(0, 2) != "FP")
                        {
                            string newFolder = newImage.Substring(2, 8);
                            string destFilename = DestinationFile + "\\" + newFolder;
                            if (!Directory.Exists(destFilename))
                            {
                                Directory.CreateDirectory(destFilename);
                            }
                            destFilename = destFilename + "\\" + newImage;
                            File.Move(fileImage, destFilename);
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                //do something??
                string str = ex.ToString();
            }
            return 0;
        }
    }
}

[Evil_Giraffe]

I don't see that you've wired up the bgWorker_ProgressChanged method to the BackgroundWorker (or the _RunWorkerCompleted method, either, whilst we're on the subject).

[mojo69]

I dropped a BackgroundWorker control on the form and named it bgWorker. Is this what you mean? I am getting updates in my label2.text control on the form? What have I done incorrectly?

Thanks,

[Evil_Giraffe]

Sorry, I had my head in VB mode so was expecting a "Handles bgWorker.ProgressChanged" on the end of the method signature. If you're getting updates in the label then you have the events wired up, but I thought that your problem was that you weren't getting updates.

Could you clarify please? (What do you expect to see? What do you actually see?)

[mojo69]

I want to move

public int ProcessImages(String SourceFolder, String DestinationFile)

into a separate class and still be able to update the label on the form. Right now I see the label2.text getting updated with the percentage calculated.

[Evil_Giraffe]

So move the method. Call it from the same place in the DoWork method via an instance of that class.

[mojo69]

Will I need to pass the backgroundworker? Or use a delegate?