Why do other UI components interfere with crossthreaded update of picturebox?

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Hello,

In the program I'm making, a picturebox's image is updated 100 times per second from another thread. The image will only show if the picturebox is the only UI element on that form. So i'm guessing I should be looking into the UI thread initialization, but I'm not sure, so I won't mess with the constructor until someone tells me it's OK to do so without risking corrupting my project.

The thing is: I need more than just a picturebox on the form; i will need buttons, textboxes etc. as well. So at the moment, the only way my program can work is if the picturebox has its own form.

Please tell me how I can get this picturebox with the other UI elements!

Regards,
Ricky F

Posted 17-Jan-14 11:55am

Rixterz123

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Ron Beyer 17-Jan-14 18:00pm

You need to post code about how you are using the picturebox so we can see what you are doing to cause problems. From your description it will be difficult to figure out what is going on.

[no name] 17-Jan-14 18:05pm

the code is just this: Picturebox1.image=bf.deserialize(client.getstream)
[where client is a tcpclient, and bf is a binaryformatter)
So it looks like it actually wasn't crossthreading, but I'm still confused about the other components interfering anyway...

Ron Beyer 17-Jan-14 18:09pm

Is this done in a separate thread? Timer?

[no name] 17-Jan-14 18:20pm

This is the whole code:
Dim ReceiveMessageClient As New TcpClient
Dim ReceiveMessageServer As New TcpListener(MessageReceiverPort)
Dim ReceiveMessageListening As New Thread(AddressOf receivemessageListen)
Dim GetMessage As New Thread(AddressOf ReceiveMessage)
Private Sub ReceiveMessage()
Try
While ReceiveMessageClient.Connected = True
Picturebox1.image = BF.Deserialize(ReceiveMessageClient.GetStream)
End While
Catch ex As Exception
End Try
End Sub
Private Sub ReceiveMessageListen()
While ReceiveMessageClient.Connected = False
ReceiveMessageServer.Start()
ReceiveMessageClient = ReceiveMessageServer.AcceptTcpClient
End While
GetMessage.Start()
End Sub

Ron Beyer 17-Jan-14 18:24pm

Have you tried putting a breakpoint in the catch and see if you are getting an exception? I'm guessing its an illegal cross thread exception, probably because the UI thread has more service work when you try to set the image.

[no name] 17-Jan-14 18:28pm

there are no errors whatsoever. When the picturebox is the only UI element on the form, it works. But when there are other UI elements on the same form as that picturebox, nothing shows up in that picturebox.

Ron Beyer 17-Jan-14 18:30pm

I would remove the try/catch and try running again, it may help clear things up. Also run outside of the debugger (open the Bin\Debug folder and double click the application).

[no name] 17-Jan-14 18:33pm

The try/catch is necessary in case the connection is cut. i'll try tomorrow

CPallini 17-Jan-14 18:27pm

100 times per second is a bit high even for a video game!

Philippe Mori 17-Jan-14 20:59pm

Try it with a slower update rate...

You should not do cross thread update without proper thread switching. For most WinForms control all update must be done from UI thread.

If you do that much update, there are chance that the application is 100% of the time busy for repainting...

Sergey Alexandrovich Kryukov 17-Jan-14 21:54pm

The problem is not clear. You should never do any cross-thread calls with UI, on all of your controls, not just PictureBox.
—SA

[no name] 18-Jan-14 9:57am

The only thing I can think that I can do now is to send you the very basic version of the program that simply tests screen sending. All you have to do is start both executables, click the connect button on both, then click "Watch screen" and it won't come up with anything. I've included a listbox to show which messages are being received. Please have a look through those 2 projects in this zip folder: http://www.datafilehost.com/d/db2cf8ce [these are not trojans; to make sure, just look through the vb code files if you would like]

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Why do other UI components interfere with crossthreaded update of picturebox?

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Why do other UI components interfere with crossthreaded update of picturebox?

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