C# isn't a database but if you're asking for a sample database for SQL Server you can try this:
http://msftdbprodsamples.codeplex.com/releases/view/55926[
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Addition:
There are lot of good examples if you google:
http://www.google.com/#hl=en&q=c%23+sample+sql+server[
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For example
Beginners guide to accessing SQL Server through C#[
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I don't think there's a complete example for all features but if you start with the basic operations (connect, select, update, close, transactions etc) you'll get a good start.
If you want you can use the sample databases (the link I posted) so you don't have to create and fill the tables in the beginning.
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