Some users type data into the field what they want instead of selecting from the list of drop down.
Is there anyway to block typing any data into a field by user? Instead I want the user to select data from a list of drop down.
You could add Validation to the field to only be one of the values in the value list you have in your drop-down list.
There are a number of ways to do what you are wanting. Mostly it will depend on how you have things designed now and what kind of user experience you want for your users. Some Options:
Beware, users can still paste into a field that has a pop-up menu.
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