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Form1.cs
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Form1.cs
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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Numerics;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace AdvancedConsoleApplicationV
{
public partial class Form1 : Form
{
#region Fields
// Monitoring for Cancellation
CancellationTokenSource m_TokenSource = null;
#endregion Fields
#region Constructors
public Form1()
{
InitializeComponent();
}
#endregion Constructors
#region Methods
/// <summary>
/// Update the pi output text box
/// update a value on the UI thread from within our task
/// </summary>
/// <param name="pi">New value for pi</param>
private void UpdatePiTextBlock(string pi)
{
// check if cross-thread synchronization is required
// check the specific control’s InvokeRequired property
// So, if UpdatePiTextBlock is called from our task, the
// test for InvokeRequired required will return
// true.This will then asynchronously call UpdatePiTextBlock
// recursively. This time, however, since it was invoked upon
// the UI thread, InvokeRequired will be false so the else
// portion of the function executes, updating the TextBox.
if (piTextBox.InvokeRequired)
{
// If this condition is true, then we need to recursively
// invoke this method on the UI thread
piTextBox.BeginInvoke(new Action<string>(UpdatePiTextBlock), pi);
} // end of if
// simply update the piTextBox with the pi value given in the method
else
{
piTextBox.Text = pi;
} // end of else
} // end of method
/// <summary>
/// Task to calculate an ever-growing number of digits in pi (up to 1,000,000)
/// task that will calculate the digits of pi by calling MathStuff.Calculate()
/// </summary>
private void CalculatePiTask()
{
try
{
for (int i = 2; i < 1000000; i++)
{
// Call ThrowIfCancellationRequested periodically to test for cancellation request
// At every iteration we will check to see if cancellation was requested
// if (m_TokenSource.Token.IsCancellationRequested) throw new OperationCanceledException();
m_TokenSource.Token.ThrowIfCancellationRequested();
// Start Time the Calculation
DateTime start = DateTime.Now;
// Calculate PI at a particular digit
string pi = MathStuff.Calculate(i);
// Update the UI
UpdatePiTextBlock(pi);
// End Time for Calculation
DateTime end = DateTime.Now;
// Total Time for the Calculation in Milliseconds
double totalMs = end.Subtract(start).TotalMilliseconds;
if (totalMs < 500)
{
// Slow down the task for visual purposes only
Thread.Sleep(500 - (int)totalMs);
} // end of if
} // end of for
} // end of try
// when the user cancels the Task
catch (OperationCanceledException)
{
Console.WriteLine("Cancelled.");
throw;
} // end of catch
} // end of method
#endregion Methods
#region Event Handlers
/// <summary>
/// Demonstrates Parallel.ForEach
/// </summary>
/// <param name="sender">object sender</param>
/// <param name="e">Event Arguments</param>
private void parallelGoButton_Click(object sender, EventArgs e)
{
// Query to Filter out ProgressBar Controls
var query = from Control child in parallelGroup.Controls
where child is ProgressBar
select child as ProgressBar;
// anonymous method that will update an individual ProgressBar
// execute the ProgressBar updates on the thread that created the controls
// If we try to update the controls from a separate thread without the
// synchronization exceptions would result.
Action<ProgressBar, int> updateProgressBarValue = delegate (ProgressBar pb, int value)
{
pb.Value = value;
}; // end of anonymous method
// iterate through the ProgressBar controls returned from “query” in a parallel manner
// lambda expression is executed once per item from “query”
// The TPL decides how to allocate threads for each iteration
Parallel.ForEach(query, progressBar =>
{
for (int i = 0; i < progressBar.Maximum; i++)
{
if (i % 100 == 0)
{
// we use the BeginInvoke method of the ProgressBar to execute
// the anonymous method stored in updateProgressBarValue
// This executes updateProgressBarValue on the thread that the ProgressBar was created on
// Because we are using a UI control’s BeginInvoke method,
// we are not required to call EndInvoke to complete the call
// using BeginInvoke instead of Invoke to avoid blocking on the call
// Delegate.Invoke: Executes synchronously, on the same thread.
// Delegate.BeginInvoke: Executes asynchronously, on a threadpool thread.
// Control.Invoke: Executes on the UI thread, but calling thread
// waits for completion before continuing.
// Control.BeginInvoke: Executes on the UI thread, and calling
// thread doesn't wait for completion.
progressBar.BeginInvoke(updateProgressBarValue, progressBar, i);
} // end of if
} // end of for
}); // End of Parallel ForEach
} // end of method, event handler for button click
/// <summary>
/// Start the pi calculation task
/// </summary>
/// <param name="sender">object sender</param>
/// <param name="e">Event arguments</param>
private void taskGoButton_Click(object sender, EventArgs e)
{
// set the buttons into the appropriate state
taskGoButton.Enabled = false;
taskCancelButton.Enabled = true;
// set the CancelationTokenSource object to a new instance
m_TokenSource = new CancellationTokenSource();
// When Tasks complete, TPL provides a mechanism to automatically
// continue execution on a WinForm or WPF UI thread.To do this
// we need a handle to the UI thread which we’ll use later
var ui = TaskScheduler.FromCurrentSynchronizationContext();
// start the Task, passing it the name of the method that
// will be the entry point for the Task and the token used for cancellation:
Task calculatePiTask = Task.Factory.StartNew(CalculatePiTask, m_TokenSource.Token);
// first continuation call will execute only when the Task completes successfully
// notifies the user by showing a message box then resetting the buttons to their
// default configuration. Notice that the last parameter to ContinueWith is “ui”.
// This tells ContinueWith to execute the lambda statements to execute within
// the context of the UI thread.No Invoke / BeginInvoke needed here.
var resultOK = calculatePiTask.ContinueWith(resultTask =>
{
MessageBox.Show("Calculation fininshed", "Task Complete", MessageBoxButtons.OK, MessageBoxIcon.Information);
taskCancelButton.Enabled = false; taskGoButton.Enabled = true;
},
CancellationToken.None,
TaskContinuationOptions.OnlyOnRanToCompletion,
ui);
// second continuation call only executes if the task is cancelled
var resultCancel = calculatePiTask.ContinueWith(resultTask =>
{
MessageBox.Show("Calculation stopped by user", "Task Cancelled", MessageBoxButtons.OK, MessageBoxIcon.Information);
taskCancelButton.Enabled = false; taskGoButton.Enabled = true;
}, CancellationToken.None, TaskContinuationOptions.OnlyOnCanceled, ui);
} // end of method
/// <summary>
/// Cancel the Task of Calculating PI
/// </summary>
/// <param name="sender">object sender</param>
/// <param name="e">Event arguments</param>
private void taskCancelButton_Click(object sender, EventArgs e)
{
// if a valid token source is available then signal
// to any listeners that the Task has been cancelled
if (m_TokenSource != null)
{
m_TokenSource.Cancel();
} // end of if
} // end of method
#endregion Event Handlers
} // end of class
} // end of namespace