​​​When getting users to choose data from a medium-long list, or to enter data that has been predefined (such as Country names), it is a good idea to use a predictive-text combo rather than a normal combo or text boxes. A good implementation of predictive-text combos will also perform a type-ahead effect, providing the user with a richer experience.

Also, predictive text boxes can be used with validation, or without. In instances where you don't mind if users add data to your collection you can turn validation off; however, to keep your collection clean, it is recommended to use validation.

Figure: Bad Example - Using a Textbox and Combo to enter list data

Figure: Good Example - Predictive-Text combo with Type Ahead

Figure: Good Example - Predictive-Text combo with and without validation

Figure: Best Example - Google search ​