If you've got an image in the Icons folder of your project and its build action is "Resource", you can refer to it like this:
<Image Source="/Icons/play_small.png" />
That's the simplest way to do it. This is the only way I could figure doing it purely from the resource standpoint and no project files:
var resourceManager = new ResourceManager(typeof (Resources));
var bitmap = resourceManager.GetObject("Search") as System.Drawing.Bitmap;
var memoryStream = new MemoryStream();
bitmap.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Bmp);
memoryStream.Position = 0;
var bitmapImage = new BitmapImage();
bitmapImage.BeginInit();
bitmapImage.StreamSource = memoryStream;
bitmapImage.EndInit();
this.image1.Source = bitmapImage;
One of the benefit of using the resource file is accessing the resources by names, so the image can change, the image name can change, as long as the resource is kept up to date correct image will show up.
Here is a cleaner approach to accomplish this:
Assuming Resources.resx is in 'UI.Images' namespace, add the namespace reference in your xaml like this: