Make the list field read only in SharePoint 2010 using Client Object Model

using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.SharePoint.Client;   namespace COM {     class Program     {         static void Main(string[] args)         {             string siteUrl = "http://serverName:46563/sites/MMS-CTH/";               ClientContext clientContext = new ClientContext(siteUrl);             Web web = clientContext.Web;             List list = web.Lists.GetByTitle("CustomList");             Field field = list.Fields.GetByTitle("Title");             field.ReadOnlyField = true;             field.Update();             clientContext.Load(field);             clientContext.ExecuteQuery();             Console.WriteLine(field.Title + " is updated successfully");             Console.ReadLine();                   }     } }