BitmapImage to byte[]

Solution 1:

To convert to a byte[] you can use a MemoryStream:

byte[] data;
JpegBitmapEncoder encoder = new JpegBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(bitmapImage));
using(MemoryStream ms = new MemoryStream())
{
    encoder.Save(ms);
    data = ms.ToArray();
}

Instead of the JpegBitmapEncoder you can use whatever BitmapEncoder you like as casperOne said.

If you are using MS SQL you could also use a image-Column as MS SQL supports that datatype, but you still would need to convert the BitmapImage somehow.

Solution 2:

You will have to use an instance of a class that derives from BitmapEncoder (such as BmpBitmapEncoder) and call the Save method to save the BitmapSource to a Stream.

You would choose the specific encoder depending on the format you want to save the image in.