I'm trying to write a loop for matching the strings with keys in the dictionary. 

I'm trying to match each and every string in the app.config file with each and every key in the dictionary. for example, there is one string called "client", I have to match this string with all the keys in dictionary. 
if the string matches, replace the value "Arizona" with string in app.config file, otherwise skip.

Can someone please suggest me in writing the loop for matching and replacing.