silverlight - where did PixelFormats and WriteableBitmap.Lock go in Silverlight3? -

A few months ago I had created some online samples such as use the WriteableBitmap class in Silverlight.

Revisiting today, with the latest Silverlight 3 installer (3.0.40624.0), the API has changed.

I have made some changes. For example, the WriteableBitmap array accessory has disappeared, but I found it in new pixel property, so instead of written:

  bmp [X]  

I can write

  bmp.Pixels [x]  

for these calls What are the same substitutions, or have it used patterns change?

  BMP = new writable bitmap (width, height, pixel format.brg 32); Bmp.Lock (); Bmp.Unlock (); Can someone work for me using the updated API?   
 
 
 If you use  lock  and  unlock  Do not do and only if the  WritabelBitmap (int, int)  constructor is not used? What things break? 
 
 It seems that this API has changed between SL3 beta and release.