C# update audit table

Question

In a C# 2010 desktop application, I need to add an audit table to an application that would be similar to the 'main' table. Basically whenever anyting is changed in the 'main' table I need to show the corresponding change in the 'audit' table. The 'audit' table will be a mirror copy of the 'main' table. The only difference is one table is called 'main' table and the other table is called the 'audit' table.

**Note these table reside in a sql server 2008 r2 database.

Would you setup a trigger? If so, can you show me the sql you would use?

Would you write C#.net 2010 code? If so, can you show me the code that would solve my problem?