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C# Process.Start Causing AccessViolationException Randomly

I have been tackling this issue for 3 months now.
Error I am Getting in Native Debugging:
"Exception thrown at 0x5A222FC2 (comct123.dll) in FileReader.exe:
0xC0000005: Access violation reading location 0x0000000C."
Normal Debug:
'System.AccessVioliationException' in System.Windows.Forms.dll
My setup is really simple:
public static Form_Interface Interface;
public static void Initialize()
{
Application.SetCompatibleTextRenderingDefault(false);
Interface = new Form_Interface();
Interface.Filesdgv.DataSource = File.SortableBindingList;
Application.Run(Interface);
}
Seems simple enough, right? No.
So basically I have a simple Event that simply opens the file using Process.Start() and no matter what I do it will randomly crash with 'System.AccessVioliationException' in System.Windows.Forms.dll here:
private void Filesdgv_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
Filesdgv.Invoke((Action)(() =>
{
try
{
int rowIndex = e.RowIndex;
if (rowIndex >= 0)
{
int columnIndex = e.ColumnIndex;
File file = (File)((DataGridView)sender).Rows[rowIndex].DataBoundItem;
switch (columnIndex)
{
case 0:
{
Process.Start(file.Location);
}
break;
}
}
}
catch
{
// This fking catch never works anyway.
}
}));
}
private void FileInterface_Load(object sender, EventArgs e)
{
foreach (string oCurrent in Directory.GetFiles(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory), "Files To Check")))
if (oCurrent.EndsWith(".pdf", StringComparison.OrdinalIgnoreCase))
new File(oCurrent.Split('\\').Last(), oCurrent);
}
It doesn't matter if I am opening files/links or anything else, it still behaves in the same way.
The link and file location is a readonly field as well.
I have many other uses for reading row data and it never crashes, even if i spam click 10000 times, It will only crash randomly with Process.Start()
Things I tried:
Using BeginInvoke
Using Invoke
Not Using Invoke/BeginInvoke
Putting File Link into a string before reading it.
Using multiple Try Catch
Recoded on another machine... same results there aswell.
I tried using File.Open (either doesn't open the file or throws same error lmao)
Tried using [HandleProcessCorruptedStateExceptions], still won't catch the exception.
Dosen't matter if i click slow or fast still 1/30 chance it happens.
Tried Putting Task.Run(() => Process.Start()); you'd think that a thread will protect you from an exception? no still crashes...
File Class looks like this:
public class File
{
public static SortableBindingList<File> SortableBindingList = new SortableBindingList<File>(new List<File>());
public readonly string fileName;
public readonly string filePath;
public void AddRow()
{
Client.Interface.Invoke((Action)(() =>
{
lock (SortableBindingList)
if (!SortableBindingList.Contains(this))
SortableBindingList.Add(this);
}));
}
public string FileName
{
get
{
return fileName;
}
}
public string Location
{
get
{
return filePath;
}
}
public File(string fileName, string filePath)
{
this.fileName = fileName;
this.filePath = filePath;
AddRow();
}
}
Initalize() is called in static void Main(string[] args) btw.
There are no other threads running editing stuff or anything like that, the only thread running is the form thread. which waits for user input.
Solutions I am looking for:
Alternative Method to launch files/hyperlinks.
A way to avoid form crashing (try catch style)
Crashes even with static data!:
Other threads running although these were not started by me.

Task.Run(() =>
{
Thread.Sleep(100);
Process.Start("https://www.youtube.com");
});
This has fixed my issues, it seems that when trying to immediately run "process.start" during a click event, the GUI unfocusing + starting a new process the exact same moment causes an Exception. (Microsoft pls fix.)

Using MutationObserver in GeckoFx with C#?

I am using GeckoFx to perform a login to a specific website. This website edits the page with new information should the login fail (or require additional authentication, such as a ReCaptcha). Unfortunately, it is vital that I have access an event when the page is updated. I have tried numerous approaches mainly
A continual check if the uri is still the same upon each login attempt and a subsequent check on the specific element in question (to see if the display: none property was changed. (This resulted in an infinite loop as it seems GeckoFx updates the page in a nonblocking way, causing the program to go into an infinite loop)
Sleeping for ~5 seconds between login requests and using the aforementioned uri check. All this did (predictably, I was grasping at straws) was freeze the browser for 5 seconds and still fail to update the page
Searching the GeckoFx codebase for a specific event when the page is updated similar to the DocumentCompleted event (no such luck).
The most common approach I have read about (and one that makes the most sense) is to use a MutationObserver. It seems that all of the answers across the internet involve injecting Javascript in order to perform the requisite task. Seeing as all of my programming background has not touched web development whatsoever, I'm trying to stick to what I know.
Here is my approach so far, unfortunately, it is not much.
public class GeckoTestWebLogin
{
private readonly string _user;
private readonly string _pass;
public GeckoWebBrowser Gweb;
public Uri LoginUri { get; } = new Uri("https://website.com/login/");
public bool LoginCompleted { get; private set; } = false;
public bool Loaded { get; private set; } = false;
public GeckoTestWebLogin(string user, string pass)
{
_user = user;
_pass = pass;
Xpcom.EnableProfileMonitoring = false;
Xpcom.Initialize("Firefox");
//this code is for testing purposes, it will be removed upon project completion
CookieManager.RemoveAll();
Gweb = new GeckoWebBrowser();
Gweb.DocumentCompleted += DocLoaded;
//right about here is where I get lost, where can I set a callback method for the observer to report back to? Is this even how it works?
MutationObserver mutationObserver = new MutationObserver(Gweb.Window.DomWindow, (nsISupports)Gweb.Document.DomObject);
}
private void TestObservedEvent(string parms, object[] objs)
{
MessageBox.Show("The page was changed # " + DateTime.Now);
}
public void DocLoaded(object obj, GeckoDocumentCompletedEventArgs e)
{
Loaded = true;
if (Gweb.Url != LoginUri) return;
AttemptLogin();
}
private void AttemptLogin()
{
GeckoElementCollection elements = Gweb.Document.GetElementsByTagName("input");
foreach (GeckoHtmlElement element in elements)
{
switch (element.Id)
{
case "username":
element.SetAttribute("value", _user);
break;
case "password":
element.SetAttribute("value", _pass);
break;
case "importantchangedinfo":
GeckoHtmlElement authcodeModal =
(GeckoHtmlElement)
Gweb.Document.GetElementsByClassName("login_modal").First();
if (authcodeModal.Attributes["style"].NodeValue != "display: none")
{
InputForm form = new InputForm { InputDescription = "Captcha Required!" };
form.ShowDialog();
elements.FirstOrDefault(x => x.Id == "captchabox")?.SetAttribute("value", form.Input);
}
break;
}
}
elements.FirstOrDefault(x => x.Id == "Login")?.Click();
}
public void Login()
{
//this will cause the DocLoaded event to fire after completion
Gweb.Navigate(LoginUri.ToString());
}
}
As stated in the above code in the comments, I am completely lost at
MutationObserver mutationObserver = new MutationObserver(Gweb.Window.DomWindow, (nsISupports)Gweb.Document.DomObject);
I can't seem to find anything in GeckoFx's source for MutationObserver that would allow me to set a callback/event/whathaveyou. Is my approach the correct way to go about things or am I left with no options other than to inject Javascript into the page?
Much appreciated, thank you in advance.
Here is my attempt at option 2 in Tom's answer:
(Added into GeckoTestWebLogin)
public void DocLoaded(object obj, GeckoDocumentCompletedEventArgs e)
{
Loaded = true;
if (Gweb.Url != LoginUri) return;
MutationEventListener mutationListener = new MutationEventListener();
mutationListener.OnDomMutation += TestObservedEvent;
nsIDOMEventTarget target = Xpcom.QueryInterface<nsIDOMEventTarget>(/*Lost here*/);
using (nsAString modified = new nsAString("DOMSubtreeModified"))
target.AddEventListener(modified, mutationListener, true, false, 0);
AttemptLogin();
}
MutationEventListener.cs:
public delegate void OnDomMutation(/*DomMutationArgs args*/);
public class MutationEventListener : nsIDOMEventListener
{
public event OnDomMutation OnDomMutation;
public void HandleEvent(nsIDOMEvent domEvent)
{
OnDomMutation?.Invoke(/*new DomMutationArgs(domEvent, this)*/);
}
}

I don't think Geckofx's webidl compiler is currently advanced enough to generate the callback constructor.
Option 1. - Enhance MutationObserver source.
You could modify MutationObserver source manually to add the necessary constructor callback. Then recompile Geckofx. (I haven't look to see how difficult this is)
Option 2. - Use old style Mutation events.
public class DOMSubtreeModifiedEventListener : nsIDOMEventListener
{
... // Implement HandleEvent
}
Then something like (maybe in DocumentCompleted event handler):
_domSubtreeModifiedEventListener = new DOMSubtreeModifiedEventListener(this);
var target = Xpcom.QueryInterface<nsIDOMEventTarget>(body);
using (nsAString subtreeModified = new nsAString("DOMSubtreeModified"))
target.AddEventListener(subtreeModified, _domSubtreeModifiedEventListener, true, false, 0);
Option 3. - Use Idle + Check.
Add an winforms Application.idle event handler - and examine the document, to know when its ready.
Option 4. - Inject a javascript callback.
(As you have already mentioned) - This example is waiting until after a resize is done.
basically inject: "<body onresize=fireResizedEventAfterDelay()>" : then inject something like this:
string fireResizedEventAfterDelayScript = "<script>\n" +
"var resizeListner;" +
"var msDelay = 20;" +
"function fireResizedEventAfterDelay() {" +
"clearTimeout(resizeListner);" +
"resizeListner = setTimeout(function() { document.dispatchEvent (new MessageEvent('resized')); }, msDelay);" +
"}\n" +
"</script>\n";
Then in the C#:
browser.AddMessageEventListener("resized", (s) => runafterImDone())

How do I return results while inside a loop in C#?

Essentially, I have a Do..While loop going through some lines from a text file. I want to process a line, return a value (worked or didn't), then move to the next line.
I have a function called ProcessTXT that accepts 2 strings. Source and Destination of new file.
Is there a way to set a ReturnedValue string = to the result and have the backgroundworker check to see if the variable changed? And if so, add this value to the list box?
private void TranslatePOD(string strSource, string strDest,)
{
TextWriter tw = new StreamWriter(strDest);
TextReader tr = new StreamReader(strSource);
do
{
//My Code doing stuff
//Need to send a result somehow now, but i have more work to do in this loop
//Then using tw.writeline() to write my results to my new file
} while (tr.ReadLine() != null);
}
EDIT: Current test code using Yield. My output is "TestingGround.Form1+d__0". Did i do something wrong?
namespace TestingGround
{
public partial class Form1 : Form
{
static IEnumerable<string> TestYield(string strSource)
{
TextReader tr = new StreamReader(strSource);
string strCurLine = System.String.Empty;
while ((strCurLine = tr.ReadLine()) != null)
{
yield return strCurLine;
}
}
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string MySource = System.String.Empty;
MySource = #"C:\PODTest\Export Script\Export\Shipment List.csv";
listBox1.Items.Add(TestYield(MySource));
}
}

Yield is typically used to return results iteratively, or streaming. There are plenty of examples online. There's one on SO for reading in a file.

It sounds like this is a good case for a producer/consumer queue. C# 4.0 introduced BlockingCollection, which is great for this. Create the blocking collection and ensure that both this process, and whatever needs to consume the results you are passing have access to it. This method can add items to the queue, and whatever is reading the results can use the Take method, which will block [wait] until there is at least one item to take out. The collection is specifically designed to work in multithreaded environments; all of the operations are logically atomic.

C# 2.0 Function does not work when call in a separate thread

I have a function to download a mailmessage as MSG file from DocuShare server. The function works perfectly when called from a main thread. However, when I call the function in a separate thread, the download fails. When I step in to the code, I can see that the function is being called, all the parameters are evaluated correctly and the return value is what I expect. Unfortunately, I see, no files get downloaded.
Codes:
private void btnDownloadMails_Click(object sender, EventArgs e)
{
//Thread t = new Thread(new ThreadStart(DownloadMailAsMsg));
//t.Start(); //Does not work
DownloadMailAsMsg(); // Works fine
}
void DownloadMailAsMsg()
{
DSServerMap.Server dsserver = new DSServerMap.Server();
if (!SelectMappedServer(ref dsserver, textServer.Text.ToString()))
return;
long status = 0;
dsserver.DocuShareAddress = textServer.Text;
dsserver.UserName = textUser.Text;
dsserver.Password = textPwd.Text;
status = dsserver.Logon();
if (status == 0)
{
IItemObj objParentItem;
string[] emailHan = { "MailMessage-12", "MailMessage-13", "MailMessage-31" };
foreach (string handnum in emailHan)
{
objParentItem = (IItemObj)dsserver.CreateObject(handnum);
DSGATEWAYLib.IGatewayHandler gateway = (DSGATEWAYLib.IGatewayHandler)dsserver.Open();
objParentItem.AttachGateway(gateway, true);
objParentItem.Name = #"D:\em\m_" + handnum + ".msg";
int flag = objParentItem.DSDownload(0);
}
}
}
Any ideas?
Thanks
Prakash

Maybe you need a STA thread for this. I had a similar problem once and the following solved my problem:
Thread t = new Thread((ThreadStart)delegate
{ // MAPI does only work in STA threads. Therefore an STA thread needs to be created explicitly for the SendMail call.
//...do work here
});
t.SetApartmentState(ApartmentState.STA);
t.Start();
Maybe this will solve your problem as well.

Your thread should be a class member instead of a method variable.
When your method completes, the thread variable goes out of scope and could get cleaned up without completing.

You are trying to access Control's properties in non UI threads,
for example in lines,
dsserver.DocuShareAddress = textServer.Text;
dsserver.UserName = textUser.Text;
dsserver.Password = textPwd.Text;
you are trying to access UI Control's Text properties in different thread, which actually throws an exception.
Each of the control's values you want to access in different thread, you have to wrap it in some sort of arguements and pass it to the thread.
class MyServerParameters{
string Server;
string Username;
string Password;
}
private void btnDownloadMails_Click(object sender, EventArgs e)
{
MyServerParameters p = new MyServerParameters();
// we are still in UI thread so copy your values
// to p
p.Server = textServer.Text;
p.Username = textUser.Text;
p.Password = textPwd.Text;
Thread t = new Thread(new ParametricThreadStart(DownloadMailAsMsg));
// pass p to another thread
t.Start(p); // this will work...
}
void DownloadMailAsMsg(object mp)
{
// access p back like this...
MyServerParameters p = mp as MyServerParameters;
dsserver.DocuShareAddress = p.Server;
dsserver.UserName = p.Username;
dsserver.Password = p.Password;

Create a copy of .Text properties of the controls and reference only them in your second thread.
You'll lock your application or get an exception if you use different thread to access any of the controls.
Other way around is to use .Invoke(), but in your case you really don't need to go there.

What's wrong with my application ---- Size was 0, but I expected 46806 !

I'm a C# programmer.
Now, I'm using the ICSharpCode.SharpZipLib.dll to create a zip file in my current project. But it occurs to me that when I click the button at the SECOND TIME to execute a function to create a zip file, the application will throw an exception, friendly and seriously told me that "Size was zero, but I expected 46086".
I'm so confused that I want to know why? When I click the button at the first time, I can do it successfully without any error.
My related codes are as follows:
internal void ThreadProc()
{
try
{
ZipHelper.CreateZip(backupZipFile, Constants.HomeConstant, true);
// do other things
}
}
The CreateZip() function's realization is as follows:
public static void CreateZip(string zipFileName, string sourceDirectory, bool recurse)
{
FastZip zip = new FastZip();
if (File.Exists(zipFileName))
{
File.Delete(zipFileName);
}
zip.CreateZip(zipFileName, sourceDirectory, true, "");
}
Now, I will show you the recursive calling process:
Call method "UpdateAppAsync" in "ActiveCheckManager" class
public void UpdateAppAsync(string masterConfig)
{
this.masterConf = masterConfig;
Thread actualThread = new Thread(new ThreadStart(UpdateApp));
actualThread.IsBackground = true;
actualThread.CurrentCulture = Thread.CurrentThread.CurrentCulture;
actualThread.CurrentUICulture = Thread.CurrentThread.CurrentUICulture;
actualThread.Start();
}
Call the UpdateApp function asynchronously, in the UpdateApp method, it will only call the UpdateDetail function simply.
private void UpdateDetail(string masterConfig, string category)
{
IUpdate worker = new HP.ActiveCheckLocalMode.UpdateEngine.UpdateManager();
worker.UpdateApp(masterConf);
}
The worker.UpdateApp will call UpdateDetail(string, UpdateCategory) only.
private void UpdateDetail(string masterConfig, UpdateCategory cat)
{
UpdateThread updateThread = new UpdateThread(this, cat);
updateThread.MasterConfig = masterConfig;
updateThread.ThreadProc();
}
That is the calling process. When I click the update button second time, it will throw an exception, can you help me? Thank you very much.

Has the first task thread finished before you start the second time?
I would imagine that File.Delete() and some items in the SharpZipLib to not respond nicelly to multithreadingly zip the same folder simultaneously to the same file.
Promote that " UpdateThread updateThread " as a private member of the "ActiveCheckManager" class, then check if it is already running from a previous click before creating a new thread.