Create a Sonar file for your solution
Here are 2 examples of project configuration files with minimal settings, depending on which runner you will use to launch the analysis (as previously said, prefer the Simple Java Runner).
C# plugins options
Every C# plugin defines its own options that can be overriden, may it be through the Sonar configuration file that you've just created or through Sonar "System Settings" web page. You will find below the pages that describe each C# plugin options: