Can WriteableBitmap only be written-to once?

Question

I'm setting an Image's Source to a WriteableBitmap, and I'm populating that WriteableBitmap using its PixelBuffer. The first time I write to it, it works. But subsequent writes are ignored. Why?

I'm using:

Stream s = myWriteableBitmap.PixelBuffer.AsStream()

(it's in a using. and I'm not getting any exceptions)

Answer 1

Following Rob Claplan's answer you should call Invalidate after performing changes to your Bitmap.