- Thread Basics
- The Downside
- Implementing Multithreading
- A Demonstration
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A Demonstration
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Figure
1. The demonstration program's form.
This simple program shows how easy it is to implement multitasking to improve program responsiveness. The code mimics a long calculation or other data processing task with a loop that runs for 10 seconds. You can run this loop either within the program's single default thread, or you can run it in a new thread created using the techniques just described. While the calculations are running you can click a button on the form to display a message box. You'll see a marked difference in how quickly that message box displays with one or two threads.
To create the demo, start a new C# windows Application project. Place four button controls one above the other on the form, with the default names button1 through button 4 top to bottom. Change the captions as shown in the figure.
Next, put the statement
using System.Threading;
at the beginning of the code along with the other using statements. Finally, add the code shown in Listing 1 to the program. When you run the program, it will be very clear how much difference a second thread can make!
Listing 1. Code for the multithreading demo program.
private void button1_Click(object sender, System.EventArgs e)
{
//Enable/disable buttons.
button1.Enabled=false;
button2.Enabled=false;
button3.Enabled=true;
button4.Enabled=false;
LongCalculationOneThread();
}
private void button2_Click(object sender, System.EventArgs e)
{
//Enable/disable buttons.
button1.Enabled=false;
button2.Enabled=false;
button3.Enabled=true;
button4.Enabled=false;
//Run in new thread.
AutoResetEvent isDone = new AutoResetEvent(false);
ThreadPool.QueueUserWorkItem(new WaitCallback(LongCalculationTwoThreads), isDone); }
private void button3_Click(object sender, System.EventArgs e)
{
MessageBox.Show("You clicked the button!");
}
private void button4_Click(object sender, System.EventArgs e)
{
this.Close();
}
private void LongCalculationOneThread()
{
// Loop for 10 seconds.
DateTime t = DateTime.Now;
t = t.AddSeconds(10);
while (t > DateTime.Now);
// Reset buttons.
button1.Enabled=true;
button2.Enabled=true;
button3.Enabled=false;
button4.Enabled=true;
MessageBox.Show("Calculations finished.");
}
private void LongCalculationTwoThreads(object state)
{
// Loop for 10 seconds.
DateTime t = DateTime.Now;
t = t.AddSeconds(10);
while (t > DateTime.Now);
//Reset buttons.
button1.Enabled=true;
button2.Enabled=true;
button3.Enabled=false;
button4.Enabled=true;
// Signal that thread is done.
((AutoResetEvent)state).Set();
MessageBox.Show("Calculations finished.");
}