Configuration Management of .NET applications

I'm looking for some advice for a way to effeciently store configurations of our applications. A place where we could store i.e. connection strings that we could use in web.config files or maybe even a way to store whole config files.

Maybe there is some kind of key value store solution that could help with that, when during build or after deployment using TFS/Jenkins we can point there and grab connection string that should be used in web.config.

My main point is to get rid of environment specific connetion strings kept in build/relase steps or scripts that are used after deployment. Just one organized place to rull them all.