One of the controls available in the Silverlight Toolkit is the AutoCompleteBox. This represents a control that provides a text box for user input and a drop-down that contains possible matches based on the input in the text box. When this is used in conjunction with RIA Services, you have a complex solution with minimum code. Before starting you must download the Silverlight Toolkit and RIA Services July 2009 preview.
The file is created. A default method called GetCustomers has been created for you:
public IQueryable<Customer> GetCustomers()
{ return this.Context.Customers; }