如何以编程方式设置实体框架代码优先的连接字符串?

I'm trying to write some code that allows me to switch between SQLCE (locally on my dev machine) and full SQL (on AppHarbor). With SQL CE, the connection string is all handled for me, but I have to construct it myself for SQL. My code so far is below, however it gives this error:I'm trying to write some code that allows me to