<p>We can use Bitmapsource object as the content of a Image control, However if I only have Bitmap object, can I use it directly, if I convert Bitmap to Bitmapsouce using the following method:</p>

<pre><code>        Bitmap bitmap = imageObjToBeConvert;
        IntPtr HBitmap = bitmap.GetHbitmap();
        result = Imaging.CreateBitmapSourceFromHBitmap
            (HBitmap,
            IntPtr.Zero,
            Int32Rect.Empty,
            BitmapSizeOptions.FromEmptyOptions());
        DeleteObject(HBitmap);
        bitmap.Dispose();
</code></pre>

<p>It take some time. Is there any way to use Bitmap directly?</p>

<p>And I found BitmapSource seems can't be released directly, Is there a sample method to release the memory immediately, after the Bitmapsouce is not used again.</p>

I think REST would make more sense than traditional RPC. Even the
Micorosft Robotics Studio runtime application model
uses REST.
The robot can consist of different resources that are identified by URI, including one for each sensor and actuator or composite abstractions thereof.
REST puts emphasis on guaranteeing what the side effects of certain methods are and also it facilitates caching, both of which can be useful for something like controlling and monitoring a distant robot. And just because you can use REST it
doesn't
have to be the HTTP protocol.
A SAFE and IDEMPOTENT method like GET, though, is good for tracking the state of the robot and polling its sensor data. You can use something like the Last-Modified header to retrieve cached sensor data that doesn't change often (e.g., humidity or light levels).
For long distances you can use relay proxies for caching.
For commands that move the robot, something like POST would be used where every such message will change the robot (e.g., turn right ). A status code can be returned indicating whether the command was immediately executed or queued for processing.
The absolute state of any resources can be set using something like PUT where multiple messages will not change things any more than just a single message (e.g., point to north pole or dim front lights to 10% brightness). This allows for reliable messaging in case of probablity of messages getting lost en route.
A new resource may be created via a POST-like operation as well, e.g., a data-collection routine and a set of parameters. The POST request can send back a CREATED result with a URI for the new resource, which can be used to DELETE when no longer needed.
A group of robots may also speak to each other using the same REST based protocol and can enjoy the same benefits.
Granted, for something simple like one person controlling a single isolated local robot, a REST API may be overkill. But for multi-user and/or unreliable-communications-channels and/or Web-scale-networking, REST is something to consider.