基于环境变量动态设置Linq到Sql的连接字符串

I need to set my connection string for Linq to Sql based on an environment variable. I have a function which will return the connection string from the web.config based on the environment variable, but how do I get Linq to always use this "dynamically created" connection string (preferably without having to specify it every time)?I need to set my connection string for Linq to