Chapter 3
Design

If you choose to rename the file, you can create a new connection string element under <connectionStrings>, and change all elements' connectionStringName attribute to your new connection string name.

That is right

A more drastic option would be to remove the LocalSqlServer entry from machine.config, and then register it again with the new connection string. Here is what you would need to write (in machine.config):

But I don't understand this sentence.

If I want to change the LocalSqlServer to some other server it can be changed in web.config. No need to change it in machine.config

Can anyone tell me what is the point raised by the Author.

The name "LocalSqlServer" is defined in machine.config. That means, even if you never define it in web.config <connectionStrings>, your app would use the default credentials from machine.config and still work.

You'll notice it says, in the first sentence, that you would have to wade through all your code, and rename all your elements that use "LocalSqlServer" to your new name. Let's say you did not want to do that. If you simply changed the connection string in that one place (machine.config), you could force all of your elements to use your new connection string without changing the name they point to.

 You are correct, of course, that there's really no need to do that, if you define "LocalSqlServer" in web.config. But the author is merely pointing out that it is possible.