Question

I want my forms application to start multiple threads to download the source code from a site in parallel.

This is just a part of the main application.

Link to the picture: http://www.abload.de/img/pic9aym7.png
I’m not allowed to post images.

    private void buttonstart_Click(object sender, EventArgs e)
    {
         //check the list below
    }

    private void buttonabort_Click(object sender, EventArgs e)
    {
         //should always could abort the process/threads. (close all webcontrols ect)
    }

1. It should start to read the numeric in the box.
2. foreach number it should open a webbrowser or httpwebrequest to download some source code and count the runs (in this example 4 runs).
   so if the website is like “http://www.bla.com/”, it should add the run to the end of the variable (http://www.bla.com/1-4).

3. Parse the source into different strings. (strWebsiteString1, strWebsiteString2, and so on. I’ll need them later)

4. if that is done, it should read some tables(from the strings) and parse them in to arrays. (same here array1[3], array2[3], for future use)
   To get the tables I think I will use htmlagilitypack.
   I’ve already coded this htmlagilitything for console. I just need to rebuild it for my forms application, and change console writeline to put it in some arrays.

   But I’m open to other/better solution.

5. All my data I’ve parsed into the arrays should now been shown in the datagridcolumns.
   Each run will get its own row.
   But when I try to add items into the comboboxcolumn, I get errors at each and every comboboxcolumn.
6. To get them in the right order and to know which browser data it is from, column1 will get the number of runs.

I’ve already tried by myself.
I get stuck with the threads respectively crossthreading.
And the datagridview makes a lot trouble too.

Do me a favour and help me to solve this problem and show me maybe show a snippet/sample what could help me.

Answer 1

This is a clear example demonstrating what I’ve stated on my comment above. It uses lock instead of Mutex but you’ll get the point. It’s a simple code using multi-threaded Job producers all adding informations to the same (locked) resource and one consumer running once every second to interact with a form control -ListBox in this case- and clear the jobs cache.

You’ll find further informations here http://www.albahari.com/threading/part2.aspx

public partial class Form1 : Form
{
    static readonly Queue<Job> queue = new Queue<Job>();

    public Form1()
    {
        InitializeComponent();
        //starts the timer to run the ProcessJobs() method every second
        System.Threading.Timer t = new System.Threading.Timer(obj => { ProcessJobs(); }, null, 5000, 1000);                
    }               

    /// <summary>
    /// Called by informations producers to add jobs to the common queue
    /// </summary>        
    private void AddJob(Job job)
    {
        lock (queue)
        {
            queue.Enqueue(job);
        }
    }

    /// <summary>
    /// Common queue processing by the consumer
    /// </summary>
    private void ProcessJobs() {            
        Job[] jobs;
        lock (queue)
        {
            jobs = queue.ToArray();
            queue.Clear();
        }
        foreach(Job job in jobs){       
            this.Invoke(new Action(delegate {
                listBox1.Items.Add(job.Name);
            }));
        }
    }

    /// <summary>
    /// Producer
    /// </summary>        
    private void JobsProducer(string name) {
        for (int i = 0; i < 10; i++)
        {
            Random r = new Random();
            System.Threading.Thread.Sleep(r.Next(1,10)*50);
            this.AddJob(new Job(string.Format("Job({0}) n.{1}", name, i)));
        }
    }

    /// <summary>
    /// Starts the jobs producers
    /// </summary>        
    private void button1_Click(object sender, EventArgs e)
    {
        for (int i = 0; i < 10; i++)
        {
            string producerName = string.Format("Producer{0}", i);
            new System.Threading.Timer(obj => { JobsProducer(producerName); }, null, 0, System.Threading.Timeout.Infinite);
        }
    }       
}

public class Job
{
    //whatever -informations you need to exchange between producer and consumer
    private string name;
    public string Name { get { return name; } }
    public Job(string name) {
        this.name = name;
    }
}  

And here you can find an example using the Dictionary to hold several jobs results:

Dictionary<string, string[]> jobs = new Dictionary<string, string[]>();
//adds an array to the dictionary
//NB: (array it's not well suited if you don't know the values or the size in advance...you should use a List<string>)
jobs.Add("jobNumber1", new string[]{"a","b"});
//gets an array from the dictionary
string[] jobNumber1;
if (!jobs.TryGetValue("jobNumber1", out jobNumber1))
     throw new ApplicationException("Couldn't find the specified job in the dictionary");