how to read/write Json on C#

//Open the file              
var stream = File.OpenText("json file.txt"); 
//Read the file              
string st = stream.ReadToEnd();                           
var jsonArray = JsonArray.Parse(st);              
foreach (var item in jsonArray)              
{                                   
JsonObject ob = new JsonObject(item);                   
foreach (var t in ob.Values)                  
{                       
JsonObject oo = new JsonObject(t);                       
foreach (var x in oo)                      
{                          
textBox1.AppendText(x.Key + " : " + x.Value + "\n");                      
}                  
}                 

KeyValuePair<string, JsonValue> pair = new KeyValuePair<string, JsonValue>("FName","Sourabh");             
KeyValuePair<string, JsonValue> pair2 = new KeyValuePair<string, JsonValue>("LName", "SInha");              
List<KeyValuePair<string, JsonValue>> list = new List<KeyValuePair<string, JsonValue>>();             
list.Add(pair);             
list.Add(pair2);                          
JsonObject jObject = new JsonObject(list);             
var stream = new StreamWriter("json out file.txt");             
            
foreach (var x in jObject)             
{               
//  textBox1.AppendText(x.Key + " : " + x.Value + "\n");                 
textBox1.AppendText(x.ToString() + "\n");                 
stream.WriteLine(x.ToString() + "\n");             
}             
JsonArray jarray = new JsonArray("item1","item2","Item3");             
foreach (var x in jarray)             
{                                 
textBox1.AppendText(x.ToString());                 
stream.WriteLine(x.ToString());             
}