Generating JSON file using dotnet

using System.Xml;
using System.IO;
using System.Web.Script.Serialization;

 public class USER
    {
        public string FirstName, LastName, Gender;       
    }

#region Convert to JSON
    JavaScriptSerializer oJavaScriptSerializer = new JavaScriptSerializer();
    USER ouser = new USER();
    ouser.FirstName = "Test First Name";
    ouser.LastName = "Test Last Name";
    ouser.Gender = "Test Gender";                   
    string strJSON = oJavaScriptSerializer.Serialize(ouser);
    if (Session["USER"] != null)
    {
        if (File.Exists(Server.MapPath(".\\FolderName\\JSON\\") + "FileName_" + Session["USER"].ToString() + ".json"))
        {
            File.Delete(Server.MapPath(".\\FolderName\\JSON\\") + "FileName_" + Session["USER"].ToString() + ".json");
        }
        File.WriteAllText(Server.MapPath(".\\FolderName\\JSON\\" + "FileName_" + Session["USER"].ToString() + ".json"), strJSON);
    }
#endregion