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Helper I
Helper I

Set field Validations in model driven powerapps form


I'm stuck with development of a power apps form.

I have a form and it collects few details as name , email, amount etc. The problem is there will be multiple email addresses. So in the form I think its difficult to add a button " Add New" near the email field and collect dynamic count of emails. If have a way to do this its very helpful.

With the no way of above, So I tried to add a text field and adding a validation like Email1,Email2,etc.

I need how to add a expression to validate as above. I saw some articles here and not resolved my question.


Thank you.


Super User
Super User

HI @sachk_1 , Have you tried business rules? Please check this:


IF you want me to build the expressions then please share complete details.


I hope this helps.

Please click Accept as solution if my post helped you solve your issue. This will help others find it more readily. It also closes the item. If the content was useful in other ways, please consider giving it Thumbs up.👍


Super User
Super User

Hi @sachk_1 ,


For simple email validation, you can use the preview feature [Link: Blog]. If you can carry out JS and get result of this field then you can then auto validate and append into your concatenated field or simply use for validation.


There are few ways I'll share, you have to pick based on what suits your use-case better:

1. Considering you are keeping a single line of text as storing multiple emails separated with ';'

You can validate using JavaScript on the particular field and if there's any error you can set Field Error / show Error as pop-up / don't save.


2. Let's consider you still need to keep individual emails separate but still capture multiple on the record, you can use sub-grid related to that entity. (Same concept like Account - Contact) with 1-N relation but if you have multiple emails on several other records then you need to make a middle entity/table for capturing emails with N:N relationship.


Hope this helps


Hi Ethan,  This is the process. This is a simple app. user enter data and for some records there will be multiple email addresses. Some records only have one. I'm not done any development using subgrid. For this concern whats the best way? using a text field or using subgrid? if have any example way please post here. Thank you.

Hi @sachk_1 ,


You will find many blogs and docs for creating sub-grid [Blog]

Here's 1 of my old project where I have implemented multiple emails to send group email. 

This is based on a sub-grid (another Table) in respect to this Table as Lookup.

It will look like this



You can use the new Table with validating email address field and if yes, you can save the email address along with the name of the person and regarding to which Record it is attached to (currently this is 1:N relation, so duplicate can be present if same email is added on other record)


For using same email on several records, create Email List and a middle table (N:N relation) so your middle table will be the sub-grid for your mail Table and Email table will be separate.

Just to describe in image in-case it confuses (Here's N:N relationship setup); 
Here "<->" represents Lookup to those tables (If Master email is changed, it affects all instances)



Here's (1:N relationship Setup):

"=" represents direct Lookup to Table A but Email will be string (If 1 email is changed, others won't be affected)



Hope this helps



I appreciate your suggestion and help me. Actually the scenarion in here is like this. This is a simple model driven app to collect data, It is like a data entry form. So when a new record is creating there will be single or multiple email addresses, these are not in our database. So What I want here is when entering data i just need to capture that input email is in correct form.


If we use email address field it allows for one email. Thats the issue.

So I try to create a multi line text field and check email1;email2 like this in correct form.


IF you have any suggestion please let me know.


Thank you.

Hi @sachk_1 ,


Since sub-grid of email address would be nice but I understand you want to maintain in a single/multi-line of text field and then compare in your Form.


I'd suggest go with JavaScript approach where you validate the email addresses in the field separated with ';' so JS can check the structure of the email address and if any email is incorrect to throw FieldError on that field.

This is simple approach to check if entered emails in the field are valid or not.


You can trigger the function for onLoad and onChange of the field.

var validateEmails = 
    Context: null,
    checkEmails: (emailString) => 
        var formContext = validateEmails.Context;
        var emails = emailString.split(';');

        // Regular expression for email validation
        var emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;

        // Validate each email address
        for (let i = 0; i < emails.length; i++) {
            var email = emails[i].trim(); // Remove leading/trailing whitespaces

            if (!emailRegex.test(email)) {
                console.error(`Invalid email address: ${email}`);
                formContext.getControl("fieldName").setNotification(`Email not Valid : ${email}`);
    execute: (executionContext) => 
        var formContext = executionContext.getFormContext();
        validateEmails.Context = formContext;
            var emailString = formContext.getAttribute("fieldName").getValue();
            if(emailString != null)

Replace your "fieldName" and execute the function "validateEmails.execute()" and pass execution context by enabling checkbox on form.


Hope this helps

Hi Thank you. Is there any article or way how i implement this JS code in model driven app? big help.

Hi @sachk_1 ,


You can check following documentations

Microsoft Documentation

This also might help

Also, here's a blog that can help with based on similar use-case [Blog Link]


Hope this helps



I didnt get this - execute the function "validateEmails.execute()" and pass execution context by enabling checkbox on form


I saved and uploaded this to web resource. Now what should i given for function name? In your code not set function right?

Because of this I got an error in form, web resource method does not exist.


Can you help me.

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