Using a Background Worker - Update a ProgressBar on the progress of a Recursive Method

Question

Hi guys,

Below is a method that I want to ship off into a background worker but I am struggling how to do it based on how created my method. As you can it doesn't return anything which is ok but it expects a directoryInfo object everytime it is recalled.

    private void getSizeForTargetDirectory(DirectoryInfo dtar)
    { 
        // generate a collection of objects. files comes first and then directories.

        foreach (Object item in collection )
        {
            if (item == file)
            {
               track the size of the files as you encounter.
            }
            else if (item == directory)
            {
                // found a new directory, recall the method. !!!
            }
        }
    }

This is my first time using a background worker so I'm a little stuck, I tried implementing something thanks to the help found here but got stuck when I realised my method was recursive.

http://stackoverflow.com/questions/1194620/c-newbie-show-progress-during-a-loop-wpf

I implemented a doWork event handler method but noticed that i needed to somehow recall the method if I had more files and folders to process on lower sub levels.

I have a simple button click event handler that calls my 'getSizeForTargetDirectory()' method when the current selected node is a directory.

 private void retrieveInfoButton_Click(object sender, EventArgs e)
    {
        // check to see if the path is valid
        // reset the labels and textfields.
        string fullPath = treeDrives.SelectedNode.FullPath;
        string sNodesName = treeDrives.SelectedNode.Text;

        if (directory) // Enter here if its a directory.
        {
            string parentPath = treeDrives.SelectedNode.Parent.FullPath;
            DirectoryInfo[] dirArray = populateFoldersArray(parentPath);

            for (int i = 0; i < dirArray.Length; i++)
            {
                if (dirArray[i].Name == sNodesName)
                {
                    getSizeForTargetDirectory(dirArray[i]);

                    // do work !

Hopefully that explains what I am trying to do and how I am doing it. Question is how can i use the report progress feature of the background worker class when the bulk of the work I am trying to ship is coming from a recursive method.

Through early testing I noticed that my getSize method was incredibly efficient after a few tweaks and reported size information for the current supplied folder very quickley but then again I use quite a powerful dev machine so this may not be true for all users.

Thanks For Reading, Hope someone can help !!!

Answer 1

I think it is much simpler to use the built-in methods on either Directory or DirectoryInfo to obtain all directories, or files, using the recursive search option:

public partial class Form1 : Form
{
    private Action<float> updateProgMethod;

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        updateProgMethod = UpdateProgress;
    }

    private void GetDirectorySizeAsync(string path)
    {
        backgroundWorker.RunWorkerAsync(path);
    }

    private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        DirectoryInfo di = new DirectoryInfo((string)e.Argument);
        di.GetTotalSize(ProgressCallback);
    }

    // Takes callbacks from the GetTotalSize() method
    private void ProgressCallback(float p)
    {
        // Invokes update progress bar on GUI thread:
        this.BeginInvoke(updateProgMethod, new object[] { p });
    }

    // Actually updates the progress bar:
    private void UpdateProgress(float p)
    {
        progressBar.Value = (int)(p * (progressBar.Maximum - progressBar.Minimum)) + progressBar.Minimum;
    }
}

public static class IOExtensions
{
    public static long GetTotalSize(this DirectoryInfo directory, Action<float> progressCallback)
    {
        FileInfo[] files = directory.GetFiles("*.*", SearchOption.AllDirectories);
        long sum = 0;
        int countDown = 0;
        for (int i = 0; i < files.Length; i++)
        {
            sum += files[i].Length;
            countDown--;
            if (progressCallback != null && countDown <= 0)
            {
                countDown = 100;
                progressCallback((float)i / files.Length);
            }
        }
        return sum;
    }
}

It's hard to guess progress without knowing the number of files or folders first!

EDIT: I've improved the code a little.

Answer 2

If, when you call a method, you don't know how long the method is going to take or how many discrete steps are going to be involved, then there is no way to display a progress bar while the method is executing.

In my opinion, the purpose of a progress bar is not to give reliable information about when a task is going to be completed. Rather, the purpose is to keep the user from freaking out and cancelling the whole operation because they think your program has locked up and isn't doing anything at all.

Since you're iterating through directories and sub-directories, a simpler approach here might be to just display the current directory in a Label. This would give the user a relaxing sense that things are happening, and if the directories are all ordered alphabetically, they can even gauge for themselves the overall progress of the operation.

Answer 3

I would report how far you have gotten since you don't know the goal until you get there. I would do it once per invocation. Perhaps # of files and # of directories seen so far.