How to perform file validation on submit button ?

There are many examples in the documentation:

https://docs.appian.com/suite/help/22.3/File_Upload_Component.html#file-upload-with-multiple-files

Hi , I already added the validation as like document but I want to show the validation message through submit button. 

Can I set the validation condition on submit button?

primaryButtons: {
      a!buttonWidget(
        label: "Submit",
        submit: true,
        style: "PRIMARY",
        loadingIndicator: true,
        validate: {
          
        }
      )
    },

What do you mean with "validation message through submit button"?

And no, the file validation only works inside the file upload field. There are some unsupported dirty hacks to do this in a different way, but I do NOT recommend this.

Okay

You Can add validation to the file upload field. 

Unknown said:

I want to show the validation message through submit button.

form-level and section-level validation messages can be shown on Submit click pretty easily using a!validaitonMessages(), which is very useful in many situations. 

However as Stefan already pointed out, there is no officially supported way to perform File Size validation outside of the File Upload Field.  And honestly something like this where a user might be required to select and wait for the upload to complete for a replacement file, that seems like the sort of use case where they probably shouldn't be forced to wait until Submit time anyway.