title: Silverlight AutoCompleteBox on custom search
body: <p>I have this object :</p>
  
  <pre><code>public class Person
  {
      public string FirstName { get; set; }
      public string LastName { get; set; }
      public string FullName
      {
          get { return string.Format("{0} {1}", FirstName, LastName); }
      }
  
      public override string ToString()
      {
          return "Person " + LastName;
      }
  }
  </code></pre>
  
  <p>And this Collecion:</p>
  
  <pre><code>public ICollection&lt;Person&gt; Persons { get; set; }
  </code></pre>
  
  <p>My AutoCompleteBox is :</p>
  
  <pre><code>&lt;sdk:AutoCompleteBox ItemsSource="{Binding Persons}" FilterMode="Contains"
                                      SelectedItem="{Binding EmployeeSelected,Mode=TwoWay}"
                                   MinimumPrefixLength="2"/&gt;
  </code></pre>
  
  <p>When i search in the Persons collection i want search by FirstName? 
  Which is the property in AutoCompleteBox for say search by FirstName?</p>