PeopleEditor is a nice webcontrol for picking people. To add it to your webpart or page is easy: But there is more we can do with pickers in Sharepoin. We can define our own pickers. Jeremy Luerkens gives one such example and a code sample (!). Another example can be found in Sharepoint as a Development Platform (p. 661), even though it misses the important class BookQueryControl. Just to start I made a book picker (I simplified and changed the idea provided in the book). Here is the working result, for simplicity the whole code is in one file: 
[sourcecode language=“csharp”] public partial class WPBookPickerUserControl : UserControl { protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { pnlBook.Controls.Add(new BookEditor() { Width = Unit.Pixel(200), MultiSelect = false}); } } } public class Book { public string Title { get; set; } public string Author { get; set; } public string Price { get; set; } public string Publisher { get; set; } } public class BookDataManager { private static Book[] _books = { new Book {Title = “SP”, Author = “John”, Price = “2€”, Publisher = “Amazon”}, new Book {Title = “JS”, Author = “David”, Price = “3€”, Publisher = “Amazon”} }; private static DataTable GetDataTable(IEnumerable books) { var table = new DataTable(); table.Columns.Add(“Title”, typeof(string)); table.Columns.Add(“Author”, typeof(string)); table.Columns.Add(“Price”, typeof(string)); table.Columns.Add(“Publisher”, typeof(string)); foreach (var b in books) { table.LoadDataRow(new string[] { b.Title, b.Author, b.Price, b.Publisher }, true); } return table; } public static DataTable ValidateBook(string key) { var books = _books.Where(c => c.Title == key).ToArray(); return GetDataTable(books); } public static DataTable SearchForBooks(string keyword) { var books = _books.Where(c => c.Title.Contains(keyword)).ToArray(); return GetDataTable(books); } public static PickerEntity ConvertFromDataRow(DataRow dr, PickerEntity pi) { pi = pi ?? new PickerEntity(); var t = dr[“Title”].ToString(); var a = dr[“Author”].ToString(); var p = dr[“Price”].ToString(); var l = dr[“Publisher”].ToString(); pi.Key = t; pi.DisplayText = string.Format("{0} ({1}), {2}", t, a, p); pi.EntityData = new Hashtable(); foreach(DataColumn col in dr.Table.Columns) { pi.EntityData[col.ColumnName] = dr[col.ColumnName]; } return pi; } } public class BookEditor : EntityEditorWithPicker { public BookEditor() { PickerDialogType = typeof (BookPickerDialog); ValidatorEnabled = true; } public override PickerEntity ValidateEntity(PickerEntity needsValidation) { var tblItem = BookDataManager.ValidateBook(needsValidation.Key); needsValidation.IsResolved = false; if (tblItem != null && tblItem.Rows.Count > 0) { needsValidation = BookDataManager.ConvertFromDataRow(tblItem.Rows[0], needsValidation); needsValidation.IsResolved = true; } return needsValidation; } } public class BookQueryControl : PickerQueryControlBase { public TableResultControl ResultControl { get { return (TableResultControl)base.PickerDialog.ResultControl; } } public BookEditor EditorControl { get { return (BookEditor)base.PickerDialog.EditorControl; } } protected override void OnPreRender(EventArgs e) { base.OnPreRender(e); base.ColumnList.Visible = false; } private DataTable CreateDataTable() { // Method variables DataColumn column; // Init data table DataTable table = new DataTable(); table.Locale = CultureInfo.InvariantCulture; // Loop visible column names foreach (string columnName in ResultControl.ColumnNames) { column = new DataColumn {DataType = typeof (string), ColumnName = columnName}; table.Columns.Add(column); } // Return table return table; } public override PickerEntity GetEntity(DataRow dr) { // No datarow provided if (dr == null) return null; var pi = new PickerEntity(); var t = dr[“Title”].ToString(); var a = dr[“Author”].ToString(); var p = dr[“Price”].ToString(); var l = dr[“Publisher”].ToString(); pi.Key = t; pi.DisplayText = string.Format("{0} ({1}), {2}", t, a, p); pi.IsResolved = true; pi.EntityData = new Hashtable(); foreach (DataColumn col in dr.Table.Columns) { pi.EntityData[col.ColumnName] = dr[col.ColumnName]; } return pi; } protected override int IssueQuery(string search, string group, int pageIndex, int pageSize) { search = (search != null) ? search.Trim() : null; if (string.IsNullOrEmpty(search)) { PickerDialog.ErrorMessage = “No search provided”; return 0; } var table = BookDataManager.SearchForBooks(search); if (table == null || table.Rows.Count == 0) { PickerDialog.ErrorMessage = “No matching books found.”; return 0; } PickerDialog.Results = table; PickerDialog.ResultControl.PageSize = table.Rows.Count; return table.Rows.Count; } } public class BookPickerDialog : PickerDialog { public BookPickerDialog() : base(new BookQueryControl(), new TableResultControl(), new BookEditor()) { DialogTitle = “Custom Book Picker Dialog”; Description = “Please select one or more books”; MultiSelect = false; } protected override void OnPreRender(EventArgs e) { var resultControl = (TableResultControl) ResultControl; var columnDisplayNames = resultControl.ColumnDisplayNames; var columnNames = resultControl.ColumnNames; var columnWidths = resultControl.ColumnWidths; columnDisplayNames.Clear(); columnNames.Clear(); columnWidths.Clear(); var cols = new string[] {“Title”, “Author”, “Price”, “Publisher”}; columnDisplayNames.AddRange(cols); columnNames.AddRange(cols); columnWidths.AddRange(new string[] { “40%”, “20%”, “10%”, “30%”}); base.OnPreRender(e); } } [/sourcecode] Of course the best way is to create separate files for each class, but don’t forget to add Safecontrol to web.config.