It is not obvious that BlogEngine.NET has a built-in syntax highlighting extension. I mean the current versions 1.3.1, I'm not sure about the old versions though. Anyway you can find it in the extensions settings, it is enabled by default.
So, if you need to paste a code snipped, just paste it in the text area and surround it with the [ code:<language>][/code ] tags
<language> may has one of the following values:
- c#
- vb
- js
- html
- xml
- tsql
- msh (Windows PowerShell script language)
It can take some other parameters, like ln for toggling line numbers, however if you set this parameter your layout will get broken for some reasons.