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

  1. #1

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

    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?

  2. #2
    .NUT jmcilhinney's Avatar
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    Re: Do I use a thread to update a label from a class?

    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.

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

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

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    .NUT jmcilhinney's Avatar
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    Re: Do I use a thread to update a label from a class?

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

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  5. #5

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

    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.
    Code:
    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;
            }
        }
    }

  6. #6
    PowerPoster Evil_Giraffe's Avatar
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    Re: Do I use a thread to update a label from a class?

    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).

  7. #7

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

    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,

  8. #8
    PowerPoster Evil_Giraffe's Avatar
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    Re: Do I use a thread to update a label from a class?

    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?)

  9. #9

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

    I want to move
    Code:
    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.

  10. #10
    PowerPoster Evil_Giraffe's Avatar
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    Re: Do I use a thread to update a label from a class?

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

  11. #11

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

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

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