How to save BitmapImage / WriteableBitmap using SaveFileDialog in Silverlight 3.0?

Question

How to save BitmapImage / WriteableBitmap using SaveFileDialog in Silverlight 3.0?

How can I write a WriteableBitmap from Silverlight to the file system, I'm not sure what to do with FileStream to make this work, it can be in the format of Bitmap, PNG, Jpeg, etc., if a commercial library is not required.
Can this be done?

Here is my SaveDialog call, below:

    Dim SaveDialog As New SaveFileDialog
    If SaveDialog.ShowDialog Then
        Try
            Using FileStream As Stream = SaveDialog.OpenFile
               ' Save Image File Code Here
            End Using
        Catch ex As Exception

        End Try
    End If

Edit

Added mention of WritableBitmap, since this is what my XAML writes, I just need to save the WriteableBitmap.Pixels property, which is a one-dimensional array of integer pixels, can this be put into the stream, and if so, how?

, , Pixel Stream , , "" , , , , , ( - ). JPEG PNG , , , , , PNGEncoding, , . BMP ?

        Dim Image As Imaging.WriteableBitmap = _Style.Image
        Dim Area As Integer = Image.PixelWidth * Image.PixelHeight
        For Raster As Integer = 0 To Area - 1
            Dim Pixel As Integer = Image.Pixels(Raster)
            Dim Bytes() = BitConverter.GetBytes(Pixel And &HFF)
            FileStream.Write(Bytes, 0, 4)
        Next