NormalizedUserName VS Username in DotNet Core

Question

I'm trying to create a custom implementation of IUserLoginStore for MongoDB and I noticed when using

UserManager<ApplicationUser> 

with the method

 var userResult = await _userManager.CreateAsync(user); 

it goes through the implementation of

GetUserNameAsync FindByNameAsync SetNormalizedUserNameAsync GetUserIdAsync 

I would like to clarify two questions:

• what's the purpose of having a NormalizedUsername and a UserName? the only difference that I could notice id that the normalizedUserName is in uppercase.

• I'm using my Implementation only to store users from an external login(Google plus), is there a way that I can omit username and NormilizedUserName since basically, I'm using the email in these three fields, I'm feeling that I'm duplicating data and it doesn't make any sense to me.

any recommendations?

Answer 1

1) Normalization stops people registering user names which only differ in letter casing.

2) No - those fields are part of the basic data model.

Answer 2

2. Yes, you can (if you really want):
   1. FindByNameAsync should search by u.Name case-insensitive (do you trust your DB settings?)
   2. GetNormalizedUserNameAsync should return user.Name.ToUpperCase()
   3. SetNormalizedUserNameAsync should do nothing

Please note that 2.1 can skip any index on name column in DB and hurt performance of your app (check your DB, again). Or cause 'client-side' execution (and again, dramatically hurt performance). Depending of your implementation.

I use such "minimized" User class only in internal enterprise systems which uses only specific OAuth provider and accepting users only from specified domain (Google Apps). This systems does not perform any search by user name and I safely throw NotImplementedException in many methods.