Install SQL Server Silently Using C# Forms Application

I have an windows application developed in C#, I need to install it on a PC which will just have the Operating System and .Net Framework installed. Now I have to give an option to install SQL Server 2008 R2 Express edition on that PC, using this windows application. I have coded for installing/uninstalling a windows service, but struck with sql server installation. could someone help me out in doing this.