Windows Phone 7 - Capture Screen

I am trying to capture the screen whilst my windows mobile application is running. I have this so far but I keep getting an ArgumentException of The parameter is incorrect. What am I doing wrong?

WriteableBitmap wb = new WriteableBitmap((int)this.ActualWidth, (int)this.ActualHeight);

wb.Render(this, null);

wb.Invalidate();

MemoryStream ms = new MemoryStream();

int h = 212;

int w = 444;

wb.SaveJpeg(ms, w, h, 0, 100); // The parameter is incorrect

BitmapImage bitmapImage = new BitmapImage();

bitmapImage.SetSource(ms);

image1.Source = bitmapImage;

The above is within my MainPage constructor.

Update

I managed to make use the great tutorial suggested by Matt.

However, it doesn't seem to capture anything from the WebBrowser.

1) Does anyone know how the native email application rend开发者_JS百科ers HTML email - what component does it use?

2) What is used to create the native applications in the Windows Phone 7 series?

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Here's another solution just published by Jeff Wilcox

http://www.jeff.wilcox.name/2011/10/screenshots-cs-how-to-capture-screenshots-of-your-app-on-your-device/

It captures screenshots at intervals you specify and then saves them to IsolatedStorage.

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Not sure on first inspection. The SaveJpeg params look okay, but not sure about the WritableBitmap..

Check here for a code example:

http://geekswithblogs.net/lbugnion/archive/2010/12/28/taking-a-screenshot-from-within-a-silverlight-wp7-application.aspx