It is very simple to use:
- copy source code from your IDE (like VisualStudio)
- paste source code into the source code box on this website: http://www.manoli.net/csharpformat/
- click on "format my code" button
- click on the "select all" button
- copy the HTML code
- go to your blog post
- switch to HTML mode (click on "Edit Html" tab)
- paste copied HTML code
There is one more thing you should do. Either add a link to "csharp.css" file (the file is available for download on the website) to template of your blogger blog or select "embed stylesheet" option before clicking on "format my code" button.
NB: You should be able to use the same tool with other blog engines or any other HTML pages.