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Question

I am new to programming world, kindly be gentle and my question is why the label control does not displaying file name one by one when it is called in for each loop. My task is to read the folder which contains more files I need to read the file name and display in the label control but it is not working well for me, it is simple for all but I am a beginner Why I don't know find how to find out the mistake?

Please find the code.

namespace ImageScanning
{
    partial class Form1
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.label1 = new System.Windows.Forms.Label();
            this.button1 = new System.Windows.Forms.Button();
            this.SuspendLayout();
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(21, 79);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(81, 13);
            this.label1.TabIndex = 0;
            this.label1.Text = "File scanning-->";
            // 
            // button1
            // 
            this.button1.Location = new System.Drawing.Point(27, 144);
            this.button1.Name = "button1";
            this.button1.Size = new System.Drawing.Size(75, 23);
            this.button1.TabIndex = 1;
            this.button1.Text = "button1";
            this.button1.UseVisualStyleBackColor = true;
            this.button1.Click += new System.EventHandler(this.button1_Click);
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(284, 262);
            this.Controls.Add(this.button1);
            this.Controls.Add(this.label1);
            this.Name = "Form1";
            this.Text = "Form1";
            this.Load += new System.EventHandler(this.Form1_Load);
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.Button button1;
    }
}

Button Click Event is:

private void button1_Click(object sender, EventArgs e)
{
     string imageloc = @"D:\Image";
     string[] files = Directory.GetFiles(imageloc);
     foreach (string file in files)
     {
          System.Threading.Thread.Sleep(1000);
          label1.Text = "File Scanning--> " + file;
          System.Threading.Thread.Sleep(3000);
          label1.Text = "";
     } 
}

Answer 1

You need to use threading, while running loop iterations, UI thread was busy and UI part is waiting for the event to complete before reflecting the change labels and other UI controls, so you need to start another thread for loop iterations then UI thread will be free to update UI.

Try this

private void button1_Click(object sender, EventArgs e)
{
    Task.Factory.StartNew(() =>
    {
         string imageloc = @"D:\Image";
         string[] files = Directory.GetFiles(imageloc);
         foreach (string file in files)
         {
             System.Threading.Thread.Sleep(1000);
             // Any UI control which you want to use within thread,
             // you need Invoke using UI thread. I have declare a method below

             ExecuteSecure(() => label1.Text = "File Scanning--> " + file);
             System.Threading.Thread.Sleep(3000);
             ExecuteSecure(() => label1.Text = "");    
         }          
    });        
}    

//---
private void ExecuteSecure(Action action)
{
    if (InvokeRequired)
    {
        Invoke(new MethodInvoker(() => action()));
    }
    else
    {
        action();
    }
}

Answer 2

Here is a sample code using the background worker process

BackgroundWorker bw = new BackgroundWorker();
public Form1()
{
    InitializeComponent();

    bw.WorkerReportsProgress = true;
    bw.DoWork += bw_DoWork;
    bw.ProgressChanged += bw_ProgressChanged;
}

void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
   label1.Text = "File Scanning --> " + e.UserState as string;     
}

void bw_DoWork(object sender, DoWorkEventArgs e)
{
    string imageloc = @"D:\Image";
    string[] files = Directory.GetFiles(imageloc);
    foreach (var item in files)
    {
       bw.ReportProgress(0, item);
       Thread.Sleep(1000);
    }
 }

protected void button1_Click(object sender, EventArgs e)
{
   if (!bw.IsBusy)
   {
       bw.RunWorkerAsync();
   }
}