Develop Reference

Find out which winforms controls are accessed from a background thread

We have built a huge winforms project, already in progress for multiple years.
Sometimes, our users get an exception which looks like this one.
The resolution of this problem seems to be:
don't acces UI components from a background thread
.
But since our project is a very big project with a lot of different threads, we don't succeed in finding all these.
Is there a way to check (with some tool or debugging option) which components are called from a background thread?
To clarify:
I created a sample winforms project with a single Form, containing two Button
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
button1.Text = "Clicked!";
}
private void button2_Click(object sender, EventArgs e)
{
Task.Run(() =>
{
button2.BackColor = Color.Red; //this does not throw an exception
//button2.Text = "Clicked"; //this throws an exception when uncommented
});
}
}
The background color of button2 is set to red when the button is clicked. This happens in a background thread (which is considered bad behavior). However, it doesn't (immediately) throw an exception. I would like a way to detect this as 'bad behavior'. Preferably by scanning my code, but if it's only possible by debugging, (so pausing as soon as a UI component is accessed from a background thread) it's also fine.

I've got 2 recommendations to use together, the first is a Visual Studio Plugin called DebugSingleThread.
You can freeze all the threads and work on one at a time (obviously the non-main-UI threads) and see each threads access to controls. Tedious I know but not so bad with the second method.
The second method is to get the steps in order to reproduce the problem. If you know the steps to reproduce it, it will be easier to see whats causing it. To do this I made this User Action Log project on Github.
It will record every action a user makes, you can read about it here on SO: User Activity Logging, Telemetry (and Variables in Global Exception Handlers).
I'd recommend you also log the Thread ID, then when you have been able to reproduce the problem, go to the end of the log and work out the exact steps. Its not as painful as it seems and its great for getting application telemetry.
You might be able to customise this project, eg trap a DataSource_Completed event or add a dummy DataSource property that sets the real Grids DataSource property and raises an INotifyPropertyChanged event - and if its a non-main thread ID then Debugger.Break();.
My gut feeling is you're changing a control's (eg a grid) data source in a background thread (for that non-freeze feel) and thats causing a problem with synchronisation. This is what happened to the other DevExpress customer who experienced this. Its discussed here in a different thread to the one you referenced.

Is your app set to ignore cross threading intentionally?
Cross-thread operations should be blowing up all the time in winforms. It checks for them like crazy in just about every method. for a starting point check out https://referencesource.microsoft.com/#System.Windows.Forms/winforms/Managed/System/WinForms/Control.cs.
Somewhere in your app, somebody might have put this line of code:
Control.CheckForIllegalCrossThreadCalls = False;
Comment that out and run the app, then follow the exceptions.
(Usually you can fix the problem by wrapping the update in an invoke, e.g., in a worker thread if you see textbox1.text=SomeString; change it to `textbox.invoke(()=>{textbox1.text=SomeString;});.
You may also have to add checking for InvokeRequired, use BeginInvoke to avoid deadlocks, and return values from invoke, those are all separate topics.
this is assuming even a moderate refactor is out of the question which for even a medium sized enterprise app is almost always the case.
Note: it's not possible to guarantee successful discovery of this case thru static analysis (that is, without running the app). unless you can solve the halting problem ... https://cs.stackexchange.com/questions/63403/is-the-halting-problem-decidable-for-pure-programs-on-an-ideal-computer etc...

I did this to search for that specific situation but of course, need to adjust it to your needs, but the purpose of this is to give you at least a possibility.
I called this method SearchForThreads but since it's just an example, you can call it whatever you want.
The main idea here is perhaps adding this Method call to a base class and call it on the constructor, makes it somewhat more flexible.
Then use reflection to invoke this method on all classes deriving from this base, and throw an exception or something if it finds this situation in any class.
There's one pre req, that is the usage of Framework 4.5.
This version of the framework added the CompilerServices attribute that gives us details about the Method's caller.
The documentation for this is here
With it we can open up the source file and dig into it.
What i did was just search for the situation you specified in your question, using rudimentary text search.
But it can give you an insight about how to do this on your solution, since i know very little about your solution, i can only work with the code you put on your post.
public static void SearchForThreads(
[System.Runtime.CompilerServices.CallerMemberName] string memberName = "",
[System.Runtime.CompilerServices.CallerFilePath] string sourceFilePath = "",
[System.Runtime.CompilerServices.CallerLineNumber] int sourceLineNumber = 0)
{
var startKey = "this.Controls.Add(";
var endKey = ")";
List<string> components = new List<string>();
var designerPath = sourceFilePath.Replace(".cs", ".Designer.cs");
if (File.Exists(designerPath))
{
var designerText = File.ReadAllText(designerPath);
var initSearchPos = designerText.IndexOf(startKey) + startKey.Length;
do
{
var endSearchPos = designerText.IndexOf(endKey, initSearchPos);
var componentName = designerText.Substring(initSearchPos, (endSearchPos - initSearchPos));
componentName = componentName.Replace("this.", "");
if (!components.Contains(componentName))
components.Add(componentName);
} while ((initSearchPos = designerText.IndexOf(startKey, initSearchPos) + startKey.Length) > startKey.Length);
}
if (components.Any())
{
var classText = File.ReadAllText(sourceFilePath);
var ThreadPos = classText.IndexOf("Task.Run");
if (ThreadPos > -1)
{
do
{
var endThreadPos = classText.IndexOf("}", ThreadPos);
if (endThreadPos > -1)
{
foreach (var component in components)
{
var search = classText.IndexOf(component, ThreadPos);
if (search > -1 && search < endThreadPos)
{
Console.WriteLine($"Found a call to UI thread component at pos: {search}");
}
}
}
}
while ((ThreadPos = classText.IndexOf("Task.Run", ++ThreadPos)) < classText.Length && ThreadPos > 0);
}
}
}
I hope it helps you out.
You can get the Line number if you split the text so you can output it, but i didn't want to go through the trouble, since i don't know what would work for you.
string[] lines = classText.Replace("\r","").Split('\n');

Try that:
public static void Main(string[] args)
{
// Add the event handler for handling UI thread exceptions to the event.
Application.ThreadException += new ThreadExceptionEventHandler(exception handler);
// Set the unhandled exception mode to force all Windows Forms errors to go through the handler.
Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException);
// Add the event handler for handling non-UI thread exceptions to the event.
AppDomain.CurrentDomain.UnhandledException += // add the handler here
// Runs the application.
Application.Run(new ......);
}
Then you can log the message and the call stack and that should give you enough information to fix the issue.

I recommend you update your GUI to handle this situation automatically for your convenience. You instead use a set of inherited controls.
The general principle here is to override the property Set methods in a way to make them Thread Safe. So, in each overridden property, instead of a straight update of the base control, there's a check to see if an invoke is required (meaning we're on a separate thread the the GUI). Then, the Invoke call updates the property on the GUI thread, instead of the secondary thread.
So, if the inherited controls are used, the form code that is trying to update GUI elements from a secondary thread can be left as is.
Here is the textbox and button ones. You would add more of them as needed and add other properties as needed. Rather than putting code on individual forms.
You don't need to go into the designer, you can instead do a find/replace on the designer files only. For example, in ALL designer.cs files, you would replace System.Windows.Forms.TextBox with ThreadSafeControls.TextBoxBackgroundThread and System.Windows.Forms.Button with ThreadSafeControls.ButtonBackgroundThread.
Other controls can be created with the same principle, based on which control types & properties are being updated from the background thread.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace ThreadSafeControls
{
class TextBoxBackgroundThread : System.Windows.Forms.TextBox
{
public override string Text
{
get
{
return base.Text;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.Text = value; });
else
base.Text = value;
}
}
public override System.Drawing.Color ForeColor
{
get
{
return base.ForeColor;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.ForeColor = value; });
else
base.ForeColor = value;
}
}
public override System.Drawing.Color BackColor
{
get
{
return base.BackColor;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.BackColor = value; });
else
base.BackColor = value;
}
}
}
class ButtonBackgroundThread : System.Windows.Forms.Button
{
public override string Text
{
get
{
return base.Text;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.Text = value; });
else
base.Text = value;
}
}
public override System.Drawing.Color ForeColor
{
get
{
return base.ForeColor;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.ForeColor = value; });
else
base.ForeColor = value;
}
}
public override System.Drawing.Color BackColor
{
get
{
return base.BackColor;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.BackColor = value; });
else
base.BackColor = value;
}
}
}
}

How to display data received from serial port in a textbox without the text disappearing in Visual Studio C#?

So, I'm trying to develop a simple application in visual C# which gets data from serial port and displays it in a textbox (to monitor temperature). I'm acquiring and displaying the data successfully, using the DataReceived event to update a global string variable and a timer to update the text field on my text box, as shown:
private void port_DataReceived_1(object sender, SerialDataReceivedEventArgs e)
{
try
{
globalVar.updateTemp = port.ReadLine(); //This is my global string
}
catch (IOException)
{
}
catch (InvalidOperationException)
{
}
catch (TimeoutException)
{
}
}
private void timer1_Tick(object sender, EventArgs e)
{
tempDisplayBox.Text = globalVar.updateTemp; //This is my textbox updating
}
The only issue I have is that the value shown in the textbox keeps flashing, making it hard to read. My timer is set to trigger every 10 ms (which should be fast enough, right?). Is there any way to make it more stable? I realize this may be a newb question, but to be fair I am a newb :) Any help is appreciated! Thanks!

Do you really need it updating every 10ms? What about every 500 ms or if not that then 100ms. 100ms will require your update method run 10 times less and therefore update 10 times less. The flickering you are expiriencing is due to the refresh speed. You could create custom method which will only update the temp only when target Label or textBox value is different than source port. But that will only sort the flickering when temp is steady, when temp will start vary it will bring back the flickering. Good luck ;-)
UPDATE
Hi I tried to reproduce the conditions and could not make my textbox nor Label flash. The way I tested it was by assigning int ntick = 0; and then increment the ++ntick; inside of the timer_tick method. The results didn't make any of the controls flash and were updated even every milisecond at some point. I also tried string.Format to put some load on the method. Is your app responsive?

The trick is to use double buffering. This way the operating system will redraw the Control off-screen, and only show the control when it is fully redrawn.
I have had the same problem, and solved it by extending the TextBox control like this:
public FastLogBox()
{
InitializeComponent();
_logBoxText = new StringBuilder(150000);
timer1.Interval = 20;
timer1.Tick += timer1_Tick;
timer1.Start();
SetStyle(ControlStyles.DoubleBuffer, true);
}
void timer1_Tick(object sender, EventArgs e)
{
if (_timeToClear)
{
_logBoxText.Clear();
_timeToClear = false;
}
if (_logQueue.Count <= 0) return;
while (!_logQueue.IsEmpty)
{
string element;
if (!_logQueue.TryDequeue(out element)) continue;
{
_logBoxText.Insert(0, element + "\r\n");
}
}
if (_logBoxText.Length > 150000)
{
_logBoxText.Remove(150000, _logBoxText.Length - 150001);
}
Text = _logBoxText.ToString();
}
public new void Clear()
{
_timeToClear = true;
while (!_logQueue.IsEmpty)
{
string element;
_logQueue.TryDequeue(out element);
}
}
public void AddToQueue(string message)
{
_logQueue.Enqueue(message);
}
}
I also use a timer and a concurrentQueue to avoid using Invoke to update the control from another thread. I also use a StringBuilder to prepare the string before putting it into the TextBox. StringBuilder is faster when building larger strings.

You can use ReadExisting() to read the whole data at a time.
You need to handle DataReceived Event of SerialPort
serialPort1.ReadExisting();
Sample:
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
String myData=serialPort1.ReadExisting();
}
Example Code: Here i would like to show you the code to Read Data(RFID Tag Code which is basically of length 12)
String macid = "";
private void DoWork()
{
Invoke(
new SetTextDeleg(machineExe ),
new object[] { macid });
macid = "";
}
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
string str1;
macid += serialPort1.ReadExisting();
if (macid.Length == 12)
{
macid = macid.Substring(0, 10);
Thread t = new Thread(new ThreadStart(DoWork));
t.Start();
}
}
public void machineExe(string text)
{
TextBox1.Text=text;
}

Thank you so much for the answers! I found a way to work around this issue:
Instead of replacing the contents of my textbox by rewriting the TextBox.Text property - which, as HenningNT implied, refreshes the control and causes the flickering - I'm now using the TextBox.AppendText method. Though, as I want to display only one line of data at a time, I use the textbox in multiline mode and the Environment.NewLine to jump to a new line before appending the text. As for the method of updating, I've gone back to using the timer because with the invoke method was crashing my application when I close the form, for some reason. Also, enabling double buffering didn't do me much good, although I guess I was doing it wrong... It still flickers a bit, but it's much better now :) I know this is not really a perfect solution (much more of a workaround), so I'll keep looking for it. If I find it, I'll be sure to update it here ;) My code:
private void timer1_Tick(object sender, EventArgs e) //Timer to update textbox
{
if (tempDisplayBox.Text != globalVar.updateTemp) //Only update if temperature is different
{
try
{
tempDisplayBox.AppendText(Environment.NewLine);
tempDisplayBox.AppendText(globalVar.updateTemp);
}
catch (NullReferenceException)
{
}
}
}

How to use event argument outside the event

I'm trying to create a custom download app. Its all working except for the download all button that cant pick up the "percent1" variable from the "DownloadProgressChangedEventArgs". I have instantiated it prior to the mainForm constructor but it wont read the changed value.
Here's the code, partially stripped since most of it isnt relevant to the question:
public partial class Main : Form
{
//Variables (not all, just the one im having issues with)
private double percentage1;
//Main form constructor
public Main(){...}
//Download File Async custom method
public void DldFile(string url, string fileName, string localPath, AsyncCompletedEventHandler completedName, DownloadProgressChangedEventHandler progressName)
{
WebClient webClient = new WebClient();
webClient.DownloadFileAsync(new Uri(url), localPath + "\\" + fileName);
webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(completedName);
webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(progressName);
}
//Button 1 click event to start download
private void btnDld1_Click(object sender, EventArgs e)
{
if (url1 != "" && Directory.Exists(localPath1))
{
_startDate1 = DateTime.Now;
DldFile(url1, fileName1, localPath1, completed1, progress1);
}
//took out the try/catch, other ifs to try and cut it down
}
//Download Progress Changed event for Download 1
public void progress1(object sender, DownloadProgressChangedEventArgs e)
{
percentage1 = e.ProgressPercentage; //THIS IS WHERE I WAS EXPECTING TO UPDATE "percentage1"
progressBar1.Value = int.Parse(Math.Truncate(percentage1).ToString());
}
//Button that starts all downloads click event where all my problems are at the moment
private void btnDldAll_Click(object sender, EventArgs e)
{
//The progress bar that should let me know the global status for all webClients
progressBarAll.Value = (
int.Parse(Math.Truncate(percentage1).ToString()) + //HERE IS MY PROBLEM
int.Parse(Math.Truncate(percentage2).ToString()) + //HERE IS MY PROBLEM
int.Parse(Math.Truncate(percentage3).ToString()) + //HERE IS MY PROBLEM
int.Parse(Math.Truncate(percentage4).ToString()) + //HERE IS MY PROBLEM
int.Parse(Math.Truncate(percentage5).ToString())) / 5; //HERE IS MY PROBLEM
//Checks if the link exists and starts it from the download button click event
if (url1 != "")
{
btnDld1.PerformClick();
}
//Continues for url2, 3, 4, 5 and else
}
}
So this is the shortest way i found of letting you know what im trying to pull off, if there's something missing please let me know, i'll try to add any info as fast as possible.
I have tried to instantiate "progress1" to try and acess its percentage1 variable, but it didnt work. I've tried doing the same thing with the webClient but didnt work either. I have used google and stackflow search to no avail. So im not sure if the question is too dumb, or there's a diferent way to look at the issue thats completely out of my mindset.
So main problem is updating the "percentage1" variable and using it.
There are other problems regarding the "progressBarAll.Value" calculation that will be solved when i can get my hands on the right value. So no need to worry about that if you see it.

Try not to think about 'using the event arguments outside the event'. Think about updating the state of your form.
Use properties to simplify the update logic:
public partial class Main : Form
{
private double percentage1;
private double percentage2;
private double percentage3;
private double percentage4;
private double percentage5;
private double Percentage1
{
get
{
return this.percentage1;
}
set
{
this.percentage1 = value;
this.UpdatePercentageAll(); // this will update overall progress whenever the first one changes
progressBar1.Value = GetValueFromPercentage(value);
}
}
private double Percentage2
// same code as for Percentage1
void UpdatePercentageAll()
{
this.PercentageAll = (this.Percentage1 + this.Percentage2 + this.Percentage3 + this.Percentage4 + this.Percentage5) / 5;
}
static int GetValueFromPercentage(double percentage)
{
return (int)Math.Truncate(percentage);
}
double percentageAll;
private double PercentageAll
{
get
{
return this.percentageAll;
}
set
{
this.percentageAll = value;
progressBarAll.Value = GetValueFromPercentage(value);
}
}
//Download File Async custom method
public void DldFile(string url, string fileName, string localPath, AsyncCompletedEventHandler completedName, DownloadProgressChangedEventHandler progressName)
{
WebClient webClient = new WebClient();
webClient.DownloadFileAsync(new Uri(url), localPath + "\\" + fileName);
webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(completedName);
webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(progressName);
}
//Button 1 click event to start download
private void btnDld1_Click(object sender, EventArgs e)
{
if (url1 != "" && Directory.Exists(localPath1))
{
this.StartDownloadFile1();
}
//took out the try/catch, other ifs to try and cut it down
}
void StartDownloadFile1()
{
this.Percentage1 = 0;
_startDate1 = DateTime.Now;
DldFile(url1, fileName1, localPath1, completed1, progress1);
}
//Download Progress Changed event for Download 1
public void progress1(object sender, DownloadProgressChangedEventArgs e)
{
this.Percentage1 = e.ProgressPercentage; // update property, not field
//this will be done in property setters
//progressBar1.Value = int.Parse(Math.Truncate(percentage1).ToString());
}
// then add similar code for other download buttons
//Button that starts all downloads click event where all my problems are at the moment
private void btnDldAll_Click(object sender, EventArgs e)
{
//Checks if the link exists and starts it from the download button click event
if (url1 != "")
{
this.StartDownloadFile1();
}
//Continues for url2, 3, 4, 5 and else
}
}
I would refactor the code even further, but I think it will be easier for you to understand if the code is closer to the original.
The main idea is to create a set of linked properties which work like mathematical functions. When writing the PercentageX properties I'm kind of saying 'let PercentageAll be the average of all percentages'. Then I have each download update it's own progress. Once any progress is updated it updates the average, and I don't have to rememver that inside the progress changed event handler.
And the last point is updating progress bars from percentage properties. It's quite straightforward: once a percentage is changed, I need to update a bar. If so, why bother writing something like
this.Percentage1 = x;
this.progressBar1.Value = (int)Math.Truncate(x);
In this case I have to remember everywhere that once I change the Percentage1 I have to update the bar. And in my example I just create a strict rule for that which is only in one place and works everytime. So I just cannot forget it. And if I need to change the rule, I need to change only one place, so again I cannot make a mistake.
The technique I demonstrate can be expressed as a well-known rule: 'one rule - one place', which means that you should try to have only single place in code that expresses each logical rule that exists in your program. It is a very important idea, I suggest you learn and use it.

How can I display multiple images in a loop in a WP7 app?

In my (Silverlight) weather app I am downloading up to 6 seperate weather radar images (each one taken about 20 mins apart) from a web site and what I need to do is display each image for a second then at the end of the loop, pause 2 seconds then start the loop again. (This means the loop of images will play until the user clicks the back or home button which is what I want.)
So, I have a RadarImage class as follows, and each image is getting downloaded (via WebClient) and then loaded into a instance of RadarImage which is then added to a collection (ie: List<RadarImage>)...
//Following code is in my radar.xaml.cs to download the images....
int imagesToDownload = 6;
int imagesDownloaded = 0;
RadarImage rdr = new RadarImage(<image url>); //this happens in a loop of image URLs
rdr.FileCompleteEvent += ImageDownloadedEventHandler;
//This code in a class library.
public class RadarImage
{
public int ImageIndex;
public string ImageURL;
public DateTime ImageTime;
public Boolean Downloaded;
public BitmapImage Bitmap;
private WebClient client;
public delegate void FileCompleteHandler(object sender);
public event FileCompleteHandler FileCompleteEvent;
public RadarImage(int index, string imageURL)
{
this.ImageIndex = index;
this.ImageURL = imageURL;
//...other code here to load in datetime properties etc...
client = new WebClient();
client.OpenReadCompleted += new OpenReadCompletedEventHandler(wc_OpenReadCompleted);
client.OpenReadAsync(new Uri(this.ImageURL, UriKind.Absolute));
}
private void wc_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
if (e.Error == null)
{
StreamResourceInfo sri = new StreamResourceInfo(e.Result as Stream, null);
this.Bitmap = new BitmapImage();
this.Bitmap.SetSource(sri.Stream);
this.Downloaded = true;
FileCompleteEvent(this); //Fire the event to let the app page know to add it to it's List<RadarImage> collection
}
}
}
As you can see, in the class above I have exposed an event handler to let my app page know when each image has downloaded. When they have all downloaded I then run the following code in my xaml page - but only the last image ever shows up and I can't work out why!
private void ImageDownloadedEventHandler(object sender)
{
imagesDownloaded++;
if (imagesDownloaded == imagesToDownload)
{
AllImagesDownloaded = true;
DisplayRadarImages();
}
}
private void DisplayRadarImages()
{
TimerSingleton.Timer.Stop();
foreach (RadarImage img in radarImages)
{
imgRadar.Source = img.Bitmap;
Thread.Sleep(1000);
}
TimerSingleton.Timer.Start(); //Tick poroperty is set to 2000 milliseconds
}
private void SingleTimer_Tick(object sender, EventArgs e)
{
DisplayRadarImages();
}
So you can see that I have a static instance of a timer class which is stopped (if running), then the loop should show each image for a second. When all 6 have been displayed then it pauses, the timer starts and after two seconds DisplayRadarImages() gets called again.
But as I said before, I can only ever get the last image to show for some reason and I can't seem to get this working properly.
I'm fairly new to WP7 development (though not to .Net) so just wondering how best to do this - I was thinking of trying this with a web browser control but surely there must be a more elegant way to loop through a bunch of images!
Sorry this is so long but any help or suggestions would be really appreciated.
Mike

You can use a background thread with either a Timer or Sleep to periodically update your image control.
Phạm Tiểu Giao - Threads in WP7
You'll need to dispatch updates to the UI with
Dispatcher.BeginInvoke( () => { /* your UI code */ } );

Why don't you add the last image twice to radarImages, set the Timer to 1000 and display just one image on each tick?

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

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.
How do I display progress during a busy loop?
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 !!!

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.

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.

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.