How To Insert FieldUser Value in Sharepoint using silverlight(Client object model)

How To Insert FieldUser Value in Sharepoint using silverlight

use following code to insert fielduser value in sharepoint

C# code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Microsoft.SharePoint.Client;
using Microsoft.SharePoint;

namespace users
{

public partial class MainPage : UserControl
{
string user;
GroupCollection Groupcoll;
ClientContext site;
List listobj;
User username               //This one is for the field user name 
 
public  MainPage()
{

InitializeComponent();
site = new ClientContext(ApplicationContext.Current.Url);

site.Load(site.Web);

listobj = cc.Web.Lists.GetByTitle("your list name");
cc.Load(listobj);
 
Groupcoll= site.Web.SiteGroups;
site.Load(Groupcoll, groups => groups.Include(group => group.Users));

site.ExecuteQueryAsync(new ClientRequestSucceededEventHandler(OnRequestSucceeded), null);

}

private void OnRequestSucceeded(Object sender, ClientRequestSucceededEventArgs args)
{

Dispatcher.BeginInvoke(datacon);
}

private void datacon()
{

    //To load all sharepoint user in combobox first
    foreach (Group Grp in Groupcoll)
    {
     UserCollection collUser = Grp.Users;
     foreach (User Usr in collUser)
    {
     user = Convert.ToString(Usr.Title);
     combobox1.Items.Add(user);
    }
    }

     //To Insert Selected Combobox user to Sharepoint list

    ListItem litem = listobj.AddItem(new ListItemCreationInformation());
    foreach (Group grp in Groupcoll)
                     {
                         UserCollection _usrcoll = grp.Users;
                         foreach (User usr in _usrcoll)
                         {
                             if (usr.Title == combobox1.SelectionBoxItem.ToString())
                             {
                                 username= usr as User;
                             }

                         }
                     }                    
    litem["Column Name"] = username;
    litem.Update();
    cc.ExecuteQueryAsync(new ClientRequestSucceededEventHandler(succed), null);
} 

private void succed(object sender, ClientRequestSucceededEventArgs arg)

 {
 } 

If you want to add multiple FieldUser Value then:

check this link

 http://stackoverflow.com/questions/9406018/add-users-to-usermulti-field-type-using-client-object-model?answertab=votes#tab-top 

Assign an list of FieldUserValue if you need to assign more than one user to the field.

    string[] users = { "domain\\johndoe", "domain\\peterpan" };
    var projectMembers = users
        .Select(loginName => FieldUserValue.FromUser(loginName))
        .ToList();

    litem["Column Name"] = projectMembers;
    litem.Update();