<extToolkit:TokenizedTextBox x:Name="_textBox"
DisplayMemberPath="FullName" //value to display
SearchMemberPath="FirstName" //value to search for when typing
ValueMemberPath="Id" //value to store in text property />
//code behind
_textBox.Text = "1;2;"; //list of object ids
_textBox.ItemsSource = new List<Email>() //use as lookup values
{
new Email() { Id = 1, FirstName = "John", LastName = "Doe", EmailAddress = "john@test.com" },
new Email() { Id = 2, FirstName = "Jane", LastName = "Doe", EmailAddress = "jane@test.com" },
};