Re: "An assembly with the same simple name has already been imported" error message - C# Discussion Boards

17-Jun-13 1:51

0. You have posted this question in Q&A - Do not repost here
1. There is a forum at the bottom of the article - the author will be better placed to help you.
2. "generate barcodes in c#" produces ~1,900,000 results in Google, please try those first

It is unlikely you'll want to use a web service if you just want barcodes. You can download barcode fonts[^] and use those directly, but you'll need to check compatibility.

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Error in WPF

Nick_Frenk16-Jun-13 21:54

16-Jun-13 21:54

hello guys, I need help, I'll explain the problem ...
I am making a wpf project that pressing a buttom let me see the video of the IP camera, only to see that the string directly to the video does not work, so I use the string of the image that is updated every time, to do this use the thread, and to avoid exceptions, use the delegates, only that at some point I will generate this error:

An unhandled exception of type 'System.StackOverflowException' in WindowsBase.dll

The point at which I generate error is as follows:

 Del Ert = new Del(setImage);
  images.Dispatcher.Invoke (ert, new object [] {images, url});

the type

Del

is my delegate:

public delegate void Del (Image images, string url);

I hope you can help me, if you need some additional information I can post it

Keith Barrow16-Jun-13 23:02

16-Jun-13 23:02

The most common way for this to happen is for an infinite recursion or loop to happen, e.g. a method calling itself (or calling itself via other method(s)) in such a way that the loop never ends. There is a stack object used by the .net framework when it executes your code (called the call execution stack), this has a finite size. Normally you enter a method (the call is pushed on the stack) and when the method exits the method is removed (popped off) from the stack. When infinite looping happens the method (or methods if a calls b calls c calls a etc) is repeatedly popped onto the stack filling it, then it overflows. As the stack is large this normally takes a few seconds though it can take even longer depending on your intervening code.

One problem with this is that the stack overflow exception doesn't necessarily happen where the actual problem is, so you might not have included the recursive code needed so we can help you in your problem.

I suggest two options:
1) Run the code until the error occurs, then open the stack trace window[^]. You'll see the calls made by your code and by reading through this you'll see the loop and hopefully where you need to break out of it.
2) Put a breakpoint on the code where you are getting the failure, then step through. At some point you'll loop round (hopefully quickly!) again you'll need to decide where you want to break out.

I'd try these two first, the first option is quicker though if you can't spot your problem then the second option will be clearer. There is a possibility that images.Dispatcher.Invoke (ert, new object [] {images, url}); is causing the loop, if ert is either directly or indirectly recursive. The other thing that might be the case (though unlikely) is that you have an non call-stack which is filling, but even this is likely to be filled by an infinite loop.

[Edit]
Me use INglish good and tipe weLL

Nick_Frenk16-Jun-13 23:56

16-Jun-13 23:56

hello I tried your solution, I put a break-point and I noticed that IF is the cycle that makes me run any code inifinite times.

public void setImage(Image images,string url)
        {
            
            if (images.Dispatcher.CheckAccess())
            {
                MessageBox.Show("ciao");
                Del ert = new Del(setImage);
                
                images.Dispatcher.Invoke(ert, new object[] { images, url });
                BitmapImage img = new BitmapImage();
                img.BeginInit();
                img.UriSource = new Uri(url);
                img.EndInit(); // Getting exception here 
                images.Source = img;
            }
            else
            {
                images.Dispatcher.BeginInvoke(new Del(setImage), DispatcherPriority.Normal,
                                                     new object[] { images, url });
                //images.Dispatcher.Invoke(new Action(Esc));
            }
        }


        public void StreamImg()
        {
            while (true)
            {
                var date = DateTime.Today.Hour;
                setImage(image1, @"http://ipaddress/jpg/image.jpg" + "?" + date);
                Thread.Sleep(1000);
             }
        }

Keith Barrow17-Jun-13 0:17

17-Jun-13 0:17

public void setImage(Image images,string url)
{
            
    if (images.Dispatcher.CheckAccess())
    {
        MessageBox.Show("ciao");
        Del ert = new Del(setImage);
            
        images.Dispatcher.Invoke(ert, new object[] { images, url }); //This calls setImage recursively
    }
    else
    {
        images.Dispatcher.BeginInvoke(new Del(setImage), DispatcherPriority.Normal,  new object[] { images, url });  //This calls setImage recursively
    }
}

See the comment parts I've made in the stripped down version of your code. This is the problem, in both branches of the if/else you recursively try to call the method.
I think you need to do the following:

public void setImage(Image images,string url)
        {
            
            if (images.Dispatcher.CheckAccess())
            {
                //Now on the dispatcher thread - can update the UI
                MessageBox.Show("ciao");
                BitmapImage img = new BitmapImage();
                img.BeginInit();
                img.UriSource = new Uri(url);
                img.EndInit(); // Getting exception here 
                images.Source = img;
            }
            else
            {
                //Not on the dispatcher thread call on dispatcher instead
                images.Dispatcher.BeginInvoke(new Del(setImage), DispatcherPriority.Normal,
                                                     new object[] { images, url });
            }
        }

Was should happen is setImage is called, if it is on the Dispatcher, fine, the UI is updated in the if block and the method exits. If the call isn't on the dispatcher the else block is executed, setImage calls itself on the dispatcher asychronously. When this call is executed, the if block is executed, the UI updated and the method exits (also exiting the call to setImage on the non-dispacther thread).

Nick_Frenk17-Jun-13 0:28

17-Jun-13 0:28

Keith, Thank you very much, with your solution the error disappears... Smile | :)

thanks for your patience!! Smile | :)

Keith Barrow17-Jun-13 0:30

17-Jun-13 0:30

No problem!

Nick_Frenk17-Jun-13 0:59

17-Jun-13 0:59

Ehm sorry, but I tried again and I noticed that no longer enters into the cycle without those commands, how i do? Confused | :confused:

Keith Barrow17-Jun-13 1:44

17-Jun-13 1:44

You going to have to put breakpoints on and check, the method should be entered at least once when streamImage calls it. You shouldn't be "cycling" as such, the code should be called once, go into the "else" block which calls the method once under the dispatcher thread (entering the if block and ending). If you need to loop then I don't understand the purpose of your code.

If you are entering the "else" block without going to the "if" It could be that you don't want the asynchronous BeginInvoke and you need a straight Invoke instead, but I don't know why you chose the async method in the first place. It may be the dispatcher is being destroyed before the async method is called, I really can't remember if this is possible, or if an exception is thrown if it does. It could also be that the Dispatcher is running something on a higher priority that is blocking your opertation, but I think this is less likely.

Can't be much more help than that I'm afraid.

Nick_Frenk17-Jun-13 2:43

17-Jun-13 2:43

the complete code is the following:

 public partial class MainWindow : Window
    {
        Thread newtrd;

        public MainWindow()
        {
            InitializeComponent();
            
        }

        public delegate void Del(Image images, string url);

        public void setImage(Image images,string url)
        {
            
            
            if (images.Dispatcher.CheckAccess())
            {
                //Del ert = new Del(setImage);
                //images.Dispatcher.Invoke(ert, new object[] { images, url });
                BitmapImage img = new BitmapImage();
                img.BeginInit();
                var date = DateTime.Today.Hour;
                img.UriSource = new Uri(url + "?" + date);
                img.EndInit(); // Getting exception here 
                img.Freeze();
                images.Source = img;
                
            }
            else
            {
                images.Dispatcher.BeginInvoke(new Del(setImage), DispatcherPriority.Normal,
                                                     new object[] { images, url });

                
                //images.Dispatcher.Invoke(new Action(Esc));
            }
        }


        public void StreamImg()
        {
            while (true)
            {
                try
                {
                    setImage(image1, @"http://ipaddress/jpg/image.jpg");
                }
                catch (Exception x)
                {
                    MessageBox.Show(x.Message.ToString() + "\n Chiudere il Programma dal pulsante Exit");
                }
                Thread.Sleep(500);
             }
        }
        
        private void button1_Click(object sender, RoutedEventArgs e)
        {
            newtrd = new Thread(new ThreadStart(StreamImg));
            newtrd.IsBackground = true;
            newtrd.Start();
        }

       

        private void button2_Click(object sender, RoutedEventArgs e)
        {
            if (newtrd.IsAlive)
            {
                newtrd.Abort();
            }
            this.Close();
        }
    }
}

I use delegates to overcome the problems of access to the thread

Pete O'Hanlon17-Jun-13 2:26

Pete O'Hanlon

17-Jun-13 2:26

Here's a little trick for you - there's no need to do cross thread access on a BitmapImage. As this class inherits from Freezable, you can simply call Freeze on the BitmapImage object before you assign it to images.Source. Your code could end up like this:

public void StreamImage()
{
  while (true)
  {
    var date = DateTime.Today.Hour;
    string url = @"http://ipaddress/jpg/image.jpg?" + date;
    BitmapImage image = new BitmapImage();
    image.BeginInit();
    image.UriSource = new Uri(url);
    image.EndInit();
    image.Freeze();
    images.Source = image;
  }
}

I was brought up to respect my elders. I don't respect many people nowadays.

CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier

Nick_Frenk17-Jun-13 2:45

17-Jun-13 2:45

i tried this solution, but I got another error: Unable to lock this Freezable.

Pete O'Hanlon17-Jun-13 3:09

Pete O'Hanlon

17-Jun-13 3:09

Ah yes. You're getting this because your Uri is still downloading the stream. If you hook into the DownloadComplete event on the BitmapImage, you can freeze the image at that point.

I was brought up to respect my elders. I don't respect many people nowadays.

CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier

Nick_Frenk17-Jun-13 3:18

17-Jun-13 3:18

Yes, i want the stream, the live stream of the my Ip-Cam...the only solution is to use the Thread... n fact, I used it with the windows form and didn't give me no error..