Json with .NET and C#?

I'm having trouble parsing Json string to Objects in C#. I'm using this: ``` JavaScriptSerilizer parser = new JavaScriptSerializer(); ``` but it doesn't recognize the JavaScriptSerilizer, and I can't add this: ``` using System.Web.Script.Serialization; ``` but it returns an error, not recognizing the "Script" in "System.Web", and I added "System.Web" in the References. Also, I found "System.Web.Extensions.dll" in "C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.0\", added it as a Reference but I get this error: ``` Could not resolve assembly "System.Web.Extensions". The assembly is not in the currently targetet framework... ``` I searched for the same file in lower version but I couldn't find it. What am I doing wrong?