Yet Another C# Blog

Suppose you've been given the task to write a function that copies the contents of one folder to another. So you set off on your merry way and come up with something like the following.


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 ThreadPoolPart4
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
// Get the Folder names, copy contents from one to the other
FolderBrowserDialog fb = new FolderBrowserDialog();
fb.ShowDialog();
string src = fb.SelectedPath;
fb.ShowDialog();
string dst = fb.SelectedPath;
// no error checking on the names, this is an example only

if (dst != src)
{
if (…

You are trying to come up to speed in C# fast. Then all of a sudden, you come across the C# Generic Type and wonder how do I master that.

Well, I've got some good news for you. You are in good company. You thought I was going to say I'll help you master generics. No, that's beyond a simple blog like mine. But, maybe I can help you become proficient. We just have to get the main learning hurdles out of the way.

Hurdle #1 - Rationale
Generic Types were added to C# in version 2.0. Now, I am not going to go into any detail on the history of C# or generics. I just mention this because the C# team decided they had a serious enough short coming in 1.1 to add this major feature. That is, many, many programmers were opting to ditch type-safety and decent performance in order to write more versatile data structures. How's that? Well, folks (MS included) were writing things like List and Queue and Stack to take "objects". Then their particular data structure co…

When I first started programming, I thought "Sleep" to be one of the most useless calls I could make. No, I'm not talking about personal habits, I'm talking about the Sleep() function.


using System.Threading;
Thread.Sleep(int milliSeconds)

We find this little "do nothing" function in C, C++, C#, VB, VB.Net, WScipt, and similar functions in other languages. And, I have since come to understand how useful and confusing "doing nothing" can be. So, let's take a look at it; I'll be focusing on the C# Sleep() function.

Sleep() simply suspends the execution of your thread for a specific period of time. It relinquishes the remainder of its time-slice and becomes "unrunnable" for a period of time. If the time period is zero, it relinquish its time-slice only if another thread is ready and waiting to run. If there are no waiting threads, and the time span is zero, the calling thread remains ready to run and therefore returns from Sleep(…

To wrap up this series of articles, I am going to make the application we've been working on do something a little more interesting. If you will recall in my first article on the subject of ThreadPool, I go over several ways to call the primary thread pool function QueueUserWorkItem and demonstrate how simple it is to multi-thread an application. In my second article, I look at a skeletal application that doesn't really do anything; it just displays messages on the console. However, and more importantly, it demonstrates some of the aspects of synchronization. You must synchronize if you are to do anything of real consequence with threads.

So, what sort of interesting things will this application do? My application will paint a pop-art picture. Actually, it will place random pixels on a PictureBox. Okay, its not that useful (or argueably that interesting), but it will demonstrate a means by which threads report progress to the GUI thread.

Let's look at the work item cl…

Let's continue looking at System.Threading.ThreadPool. In the last article, we went over some of the basic features a thread pool should have. We looked specifically at System.Threading.ThreadPool to see how to get your App threading quickly. And, we touched on some aspects missing from Microsoft's thread pool implementation that are needed for an "industrial strength" application. So today, we will examine some of those missing features.

Let's start with a skeleton application. This application starts a master work item that is responsible for feeding service work items to the thread pool. The service work items do some work (right now, they display a message with Console.WriteLine(...) and then sleep a random amount of time in the sub-second range). We get a taste of synchronization with the shared random number generator where I surround it with a lock(...){ } statement to make it thread safe. When service work items are done, they exit. "Exit&qu…

The System.Threading.ThreadPool is a great little feature for programmers wishing to add instant threading to their applications. You just enqueue callback functions, what could be more simple than that? I agree, so we'll look now at some simple coding experiments with the ThreadPool. By the way, here's the MSDN version of "How to: Use a Thread Pool" which makes for some good pre-requisit reading. And though I risk repeating much of what may be already elsewhere on the web, I hope that I can add something of use in your estimation.

So first, let's get a basic understanding of thread pooling. Maybe you've already read my article, Thread Synchronized Queing. If so, you have a good start. A thread pool, like my SynchQueue class, will involve some thread(s) writing to a queue, and some set number of threads reading from the queue. Similarly, if there isn't enough work to do, the reader threads wait or block on the queue. And, if there is too much work…