WFFM enable custom field type for username in "Create User" save action

Question

Is there some way to enable a custom WFFM field to be used for the username in the "Create User" save action? The dialog is shown here:

I've tried looking at the xaml file for this dialog (\Website\sitecore\shell\Applications\Modules\Web Forms for Marketers\Dialogs\Action Editor\CreateUser.xaml.xml) and the associated code-behind (Sitecore.Forms.Shell.UI.Dialogs.CreateUserPage, Sitecore.Forms.Core) but cannot see any way to customise what field types are accepted. I noticed that the allowed types for a password are configurable via query parameter, but cannot see any reference to the NameField dropdown in the code-behind.

Answer 1

The answer lies in a base class of CreateUserPage. This class inherits AuditMembershipActionPage which inherits MemberhipActionPage. MemberhipActionPage has a property called UserNameAllowedTypes which appears to read a query string parameter but defaults to a set list of field type IDs.

In order to supply the necessary query string parameter, I created a new save action as a copy of the OOTB "Create User" save action. The only thing I changed was to modify the "Editor" field to include query string parameters ?UserNameAllowedTypes=%7B88CECAB3-B76C-4E77-9255-DE5916334B8D%7D where 88CECAB3-B76C-4E77-9255-DE5916334B8D is the ID of my custom field type.