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jimfred on 07/06/10

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Last Edited at 07/06/10 01:23pm

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Modal Progress dialog with cancel for time-consuming operations, C#, WinForms

/ Published in: C#

Features/Requirements:\r\n\r\n[1] lightweight, easy-to-add\r\n[2] Display progress of long operation using (a) progress bar and (b) user-text.\r\n[3] Close dialog upon (a) Normal completion of long operation or (b) Cancel button used for early cancellation of long operation\r\n[4] GUI not hung/hourglassing during long operation. This can be done using threads or DoEvents. This example uses the BackgroundWorker class as a member of a Form.\r\n[5] Synchronized with no race conditions.\r\n\r\nThe form displayed consists of three elements: label, progress bar and a cancel button. The label auto-sizes so that user text will be displayed. The application constructs the dialog with parameters for titlebar text and a delegate for the long operation. The long operation reports progress using BackgroundWorker.ReportProgress. The long operation checks for cancellation using BackgroundWorker.CancellationPending\r\n\r\nSee code for example usage.

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// Example usage:
      private void button4_Click(object sender, EventArgs e)
      {
         // Create dialog.
         ProgressWithCancel dlgProgress = new ProgressWithCancel( "Testing progress", LongOperation);

// Show dialog with Synchronous/blocking call.
         // LongOperation() is called by dialog.
         dlgProgress.ShowDialog(); // Synchronous/blocking call.
      }

private void LongOperation(object sender, DoWorkEventArgs e)
      {
         BackgroundWorker worker = sender as BackgroundWorker;

int max = 20;
         for (int i = 0; i < max; i++)
         {
            if (worker.CancellationPending) // See if cacel button was pressed.
            {
               System.Threading.Thread.Sleep(2000); // Similate time for clean-up.
               break;
            }
            
            int percent = i * 100 / max;

string userState = percent.ToString(); // render a string to display on the progress dialog.

// Append to string just to show multi-line user-status info.
            if (percent >= 45 && percent <= 55) { userState += "Half way"; }
            if (percent >= 85) { userState += "Almost done"; }

worker.ReportProgress(percent, userState); // Report percent and user-status info to dialog.

System.Threading.Thread.Sleep(800); // Simulate time-consuming operation
         }
      }

// Implementation (in ProgressWithCancel.cs)

namespace ProgressWithCancel
{
   public partial class ProgressWithCancel : Form
   {
      public ProgressWithCancel(string whyWeAreWaiting, DoWorkEventHandler work)
      {
         InitializeComponent();
         this.Text = whyWeAreWaiting; // Show in title bar
         backgroundWorker1.DoWork += work; // Event handler to be called in context of new thread.
      }

private void btnCancel_Click(object sender, EventArgs e)
      {
         label1.Text = "Cancel pending";
         backgroundWorker1.CancelAsync(); // Tell worker to abort.
         btnCancel.Enabled = false;
      }

private void Progress_Load(object sender, EventArgs e)
      {
         backgroundWorker1.RunWorkerAsync();
      }

private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
      {
         progressBar1.Value = e.ProgressPercentage;
         label1.Text = e.UserState as string;
      }

private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
      {
         Close();
      }

}
}

// Designer (in ProgressWithCancel.designer.cs)
namespace ProgressWithCancel
{
   partial class ProgressWithCancel
   {
      /// <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.tableLayoutPanel1 = new System.Windows.Forms.TableLayoutPanel();
         this.btnCancel = new System.Windows.Forms.Button();
         this.progressBar1 = new System.Windows.Forms.ProgressBar();
         this.backgroundWorker1 = new System.ComponentModel.BackgroundWorker();
         this.label1 = new System.Windows.Forms.Label();
         this.tableLayoutPanel1.SuspendLayout();
         this.SuspendLayout();
         // 
         // tableLayoutPanel1
         // 
         this.tableLayoutPanel1.AutoSize = true;
         this.tableLayoutPanel1.ColumnCount = 1;
         this.tableLayoutPanel1.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle(System.Windows.Forms.SizeType.Percent, 100F));
         this.tableLayoutPanel1.Controls.Add(this.label1, 0, 0);
         this.tableLayoutPanel1.Controls.Add(this.btnCancel, 0, 2);
         this.tableLayoutPanel1.Controls.Add(this.progressBar1, 0, 1);
         this.tableLayoutPanel1.Dock = System.Windows.Forms.DockStyle.Fill;
         this.tableLayoutPanel1.Location = new System.Drawing.Point(0, 0);
         this.tableLayoutPanel1.Name = "tableLayoutPanel1";
         this.tableLayoutPanel1.RowCount = 3;
         this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle());
         this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle());
         this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle());
         this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Absolute, 20F));
         this.tableLayoutPanel1.Size = new System.Drawing.Size(292, 99);
         this.tableLayoutPanel1.TabIndex = 0;
         // 
         // btnCancel
         // 
         this.btnCancel.Anchor = System.Windows.Forms.AnchorStyles.Top;
         this.btnCancel.AutoSize = true;
         this.btnCancel.Location = new System.Drawing.Point(108, 60);
         this.btnCancel.Name = "btnCancel";
         this.btnCancel.Size = new System.Drawing.Size(75, 27);
         this.btnCancel.TabIndex = 0;
         this.btnCancel.Text = "Cancel";
         this.btnCancel.UseVisualStyleBackColor = true;
         this.btnCancel.Click += new System.EventHandler(this.btnCancel_Click);
         // 
         // progressBar1
         // 
         this.progressBar1.Anchor = ((System.Windows.Forms.AnchorStyles)((System.Windows.Forms.AnchorStyles.Left | System.Windows.Forms.AnchorStyles.Right)));
         this.progressBar1.Location = new System.Drawing.Point(3, 34);
         this.progressBar1.Name = "progressBar1";
         this.progressBar1.Size = new System.Drawing.Size(286, 20);
         this.progressBar1.TabIndex = 1;
         // 
         // backgroundWorker1
         // 
         this.backgroundWorker1.WorkerReportsProgress = true;
         this.backgroundWorker1.WorkerSupportsCancellation = true;
         this.backgroundWorker1.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.backgroundWorker1_RunWorkerCompleted);
         this.backgroundWorker1.ProgressChanged += new System.ComponentModel.ProgressChangedEventHandler(this.backgroundWorker1_ProgressChanged);
         // 
         // label1
         // 
         this.label1.Anchor = ((System.Windows.Forms.AnchorStyles)((((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom)
                     | System.Windows.Forms.AnchorStyles.Left)
                     | System.Windows.Forms.AnchorStyles.Right)));
         this.label1.AutoSize = true;
         this.label1.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
         this.label1.Location = new System.Drawing.Point(3, 3);
         this.label1.Margin = new System.Windows.Forms.Padding(3);
         this.label1.Name = "label1";
         this.label1.Padding = new System.Windows.Forms.Padding(3);
         this.label1.Size = new System.Drawing.Size(286, 25);
         this.label1.TabIndex = 1;
         this.label1.Text = "label1";
         this.label1.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;
         // 
         // Progress
         // 
         this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 16F);
         this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
         this.AutoSize = true;
         this.AutoSizeMode = System.Windows.Forms.AutoSizeMode.GrowAndShrink;
         this.ClientSize = new System.Drawing.Size(292, 99);
         this.ControlBox = false;
         this.Controls.Add(this.tableLayoutPanel1);
         this.Name = "Progress";
         this.StartPosition = System.Windows.Forms.FormStartPosition.CenterParent;
         this.Text = "Progress";
         this.Load += new System.EventHandler(this.Progress_Load);
         this.tableLayoutPanel1.ResumeLayout(false);
         this.tableLayoutPanel1.PerformLayout();
         this.ResumeLayout(false);
         this.PerformLayout();

}

#endregion

private System.Windows.Forms.TableLayoutPanel tableLayoutPanel1;
      private System.Windows.Forms.Button btnCancel;
      public System.Windows.Forms.ProgressBar progressBar1;
      public System.ComponentModel.BackgroundWorker backgroundWorker1;
      private System.Windows.Forms.Label label1;
   }
}

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