How to make the field optional 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.Required = false;
            field.Update();
            clientContext.Load(field);
            clientContext.ExecuteQuery();
            Console.WriteLine(field.Title + " is updated successfully");
            Console.ReadLine();           
        }
    }
}