Hi Joao,

Who creates the users? And what do you mean by "changing the index"?

Users can't have the same username as another user, unless they have a different user provider. Is that the case?

Hi João,

Try something like this in the Submit action of the form, when creating a new User

Hi Joao,

Of course it's not possible to have duplicate usernames, so is your question why that is, or how you can check on duplicates (if the latter, see André's post)?

If you are doing something like asking the user for their username at registration time then you should use the form validation and check if the user exists and ask the user to enter a different name. See Input Validation for some details on input validation.

Another option is to encourage users to use a username that would be unique anyway. Email address is a very good one as they have to be unique to start with. Still do the checks above though to trap situations where a user is trying to register twice plus your field validation should check for a valid email. Also good idea to allow a user to edit their username at a later date is some users do change email addresses occasionaly

Hi Kilian,

I was also running into this problem. In our environment, we have multiple developers creating various applications, and each app takes care of creating a user. There's nothing stopping App 1 creating username = "newuser", and App 2 creating username = "newuser". App 1 and App 2 both use the same user provider... specifically the default "Users" user provider. So it IS possible to have duplicate usernames within the same user provider.

Is it by design that the User.Username attribute has no uniqueness constraint? 

I would imagine we don't want the following:

userid = 1, username = "newuser", roles = (App1_RegularUser)

userid = 2, username = "newuser", roles = (App2_Admin)

But instead, we should have:

userid = 1, username = "newuser", roles = (App1_RegularUser, App2_Admin)

Is this the correct thinking?