programatically install sqlexpress2008 with instance name password and user id ?

Hello

I need below.

1-) if there is sqlserver2008 express, i should install instance name as myprojectname. (Programatically Csharp codes)

2-) if there is no sqlserver 2008 express, i should install sqlserver2008 and instance name as myprojectname. (Programatically Csharp Codes)

both of them my connection string should be like user id = sa; password = sa123; datasource= .\myprojectname.

Thanks.