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Field validation formula for numbers and special characters, exclude alpha characters

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Posted on by mhurston

Hello. I'm trying to write a validation formula for a field that should only accept numbers (0-9) and these special characters ("$", "%", ",", "."). Could someone please advise me on how I could exclude alpha characters from the field? There is no expected number of characters for the text entered into the field. I just want to prevent people from adding alpha character text narrative. The field needs to be restricted to numbers only, but has to be able to accept currency, percentages, integers, and floats. I believe I should be using the IsMatch function, but I'm unsure of the full expression.

Here's what I have, but it's not working.

If(IsMatch(DataCardValue4.Text,"^([a-zA-Z])$"),false,true)

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Building Power Apps

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BCBuizer 22,505 Super User 2025 Season 2 on at

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Hi,

Can you describe what is not working?

Having a quick look at the formula, it seems to be reversing the result: In case the IsMatch returns a true, the If returns a false. Given that IsMatch returns a boolean on its own, there's no need for the If function, so you can try:

IsMatch(TextInput10.Text,"^[0-9$%,.]+$")

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mhurston 14 on at

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Hi. Thanks for your help. It keeps saying there's an error in the formula for data type:boolean.

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BCBuizer 22,505 Super User 2025 Season 2 on at

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Hi @mhurston ,

Are you sure DataCardValue4 is a text input control? Also, what property are you trying to set?

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mhurston 14 on at

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Hi. @BCBuizer. This is my 1st powerapp, so I'm a novice, but I believe datacardvalue4 is text input control. I'm trying to set the default data property.

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BCBuizer 22,505 Super User 2025 Season 2 on at

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Hi @mhurston ,

Unfortunately the Default property is not meant for input validation, but rather to set a default value in case the form is in new mode.

In this blog you can find an example on how to perform data validation which I hope is useful to you:

https://www.matthewdevaney.com/data-validation-for-power-apps-forms/#Data-Validation-With-Pattern-Matching

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mhurston 14 on at

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Thank you so much @BCBuizer. That did the trick for me. I was able to get my field set up. I appreciate you!

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