Is it possible to change a form value during the UmbracoFormsController.FormValidate event? I have a hidden form field that needs to get populated with a formatted string based on other field entries.

Can you provide a small code snippet for this?

I've tried returning the field and setting its Values property, but that doesn't work.

var field = e.Form.AllFields.SingleOrDefault(f => f.Alias == "key");
field.Values = new List<object> { "test" };

It does set the value during the request, but does not save to DB or fill in the form field when posting back (on model validation error).