Share on FacebookShare is a new extension for BlogEngine.NET. What it does is pretty simple, it adds a “Share on Facebook” link on top of every post, so you can share them on facebook as a link.
After you install this extension (instructions below), you will see the link as follows
The extension uses a custom page for its configuration, where you can select the text of the link, and the link type, as explained on facebook’s help page.

And, as advertised, when you click the share link, you get the pop up window to post the link to your facebook profile

Optionally, you can add a link to the head section of the site.master of your theme, to have facebook pull that image as a thumbnail, you do that like this
<link rel="image_src" href="<your_url>" />
Where <your_url>, is the url of the image you want to display.
To install this extension, simple unzip the following files on your BlogEngine.Web root directory
Important Note: This code is an extension for BlogEngine.net version 1.4.5.15 and up. It was tested on this version, because it has a bug fix that made extensions don't work. The bug is present in 1.4.5, I don't really know exactly in which subversion it was fixed, you can check it yourself.
The problem was in the method DataStoreExtension in App_Code\ExtensionManager\Manager.cs, the line
Stream stm = (FileStream)xs.GetSettings();
has to be
Stream stm = (FileStream)o;
That's it! You can download the files below, and you can try it on this very post, just click "Share on Facebook" there on the top