Changing the current culture of the application on the fly does not affect the UI components of the current page. Consider the following scenario: the user selects a preferred language from a list. The application changes the current culture dynamically on the fly:

CultureInfo.CurrentCulture = someCulture;
CultureInfo.CurrentUICulture = someCulture;

This does not update the UI of the current page in any way. All of the UI components are displayed with the language of the original culture. The only way to see them translated to the new language is to reload the entire page.