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Old March 23rd, 2008, 01:25 PM
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Default cross thread exception

hi all!

I'm trying to create a utility that captures an image of a webpage based on the HTML from the source. I did some diging around and found that Windows Live makes an API with that functionality built in :) But when i try and use it i get the following error.

Code:
Uri uri = new Uri("http://www.msn.com");
WindowsLive.Writer.Api.HtmlScreenCapture hsc = new HtmlScreenCapture(uri, 800);

pictureBox1.Image = hsc.CaptureHtml(1000);

Error:
System.InvalidOperationException: Cross-thread operation not valid: Control '' accessed from a thread other than the thread it was created on.

The line 'pictureBox`' refers to a control i have on my windows form.

When i call the basic
hsc.CaptureHtml(1000);

it returns the same error...

any ideas are welcome... Thanks in advance

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Old March 23rd, 2008, 06:46 PM
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Default

How is this block of code being called? Is this code being called from some other thread you created or in asynchronous operation?

This is the error you typically see if you spin off your own secondary threads (manually or use a "BackgroundWorker") to perform work that is trying to manipulate controls. The controls are "owned" by the initial/primary thread (this is the UI thread). No other thread can make changes to the controls created on the UI thread. You need to transition calls back to the UI thread to do this. This is usually done by calling the Invoke method on the form class that holds the control you want to change. The Invoke method invokes the handler provided to it on the thread it was created on, thus transitioning the control manipulation call back to the proper thread.

-Peter
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