ClientPeoplePicker in SharePoint 2013

Start using SharePoint 2013 I noticed that the way for selecting people or groups is changed.
The new way is simple – just ‘Enter name or email address’ without any icons for ‘Check Names’ or ‘Browse’. I guess that the PeoplePicker is changed but NO. PeoplePicker sitll has the same functionality as before.
There is a new control called ClientPeoplePicker.

How to use it:
1. Add this references

<%@ Register TagPrefix="wssawc" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

2. Add the following control declaration

      <wssawc:ClientPeoplePicker

        Required="true"

        ValidationEnabled="true"

        ID="peoplePicker"

        runat="server"

        InitialHelpText="<%$Resources:wss,aclinv_PickerIntialHelperText%>"

        VisibleSuggestions="3"

        Rows="1"

        AllowMultipleEntities="false"

        CssClass="ms-long ms-spellcheck-true" />

3. Form server side:
      a. Set SPUser to the control

SPUser assignToUser = GetYourSPUser();

if (assignToUser != null)

{

  PeopleEditor pe = new PeopleEditor();

  PickerEntity entity = new PickerEntity();

  entity.Key = assignToUser.LoginName;

  entity = pe.ValidateEntity(entity);

  entity.IsResolved = true;

  peoplePicker.AddEntities(new List<PickerEntity> { entity });

}

     b. Get selected user

SPUser user = null;

ArrayList resolvedEntities = peoplePicker.ResolvedEntities;

foreach (PickerEntity entity in resolvedEntities)

{

   string loginName = entity.Key;

   user = site.RootWeb.EnsureUser(loginName);

   break;

   // the picker in my sample is in single mode!

}

I developed this code reviewing the mngsiteadmin.aspx - the page for editing Site Collection Administrator. As a rule - always choose the simplest pages from the SharePoint default functionality for reverse enginiring.