How to extract key values from a JSON String.

In my iOS code in Xamarin I am getting a json string in response from the Rest API and its structure is like bellow.

{ "base": "gdps stations", "id": 1269515, "name": "Jaipur", "weather": [ { "description": "haze", "icon": "50n", "id": 721, "main": "Haze" } ], "wind": { "deg": 70, "speed": 2.1 } }

How can I use this string and extract values for the some key ? May be I can save this string in a dictionary and use that to get the key value. (Please specify which name space I need to use and what assembly I need to add )