What are the prerequisites for using SQL and LINQ with my winforms application in C#?
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Specifically if I have a server that I want to use my SQL database with do I have to install an SQL database on each server computer? Can I bundle it with the software installation? If I want to utilize LINQ, am I limited to using MSSQL? 

On the same note, my database data must be secure. Is there a way I can insure only my program will be able to modify/query my programs database?
