how can i change a text box to a drop down control or vice versa?

 Hi All.
I have a drop down which has the countries of the world, i also have a dropdown for states i.e all the states. Now, depending on the selection made in the country drop down, the dropdown may need to change to a textbox or the textbox might need to change to a drop down. How can i achieve this? The only way i thought of is to have a multi view.
Any ideas?

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