DisplayName - 'User' + UserId - Best Way to Do This

Question

I want to do something like SO does with DisplayName. When someone does not enter a DisplayName, I want to default this to 'User' + UserId. So the first user who signs up would get User1 - since UserId will be 1, the second User2 - since UserId will be 2, and so on.

The easiest way I can think of doing this is using a trigger, but I don't like triggers. I could save the user, then update the user after the save (basically a trigger, but done in my code). Any other ideas on how I can handle this? Is there a way I can set the default value on the column in the database?

I am using Asp.Net MVC 2, C# 4, EF4, and SQL Server 2008.

Answer 1

You can set the user name in the stored procedure. if a user name has been passed to stored procedure, simply save it. otherwise, get the primary key id of the last entered user and add 1 to it. format it to whatever you like (e.g. User + newID) and save this as the new user's user name.

Answer 2

You can have a computedColumn

[UserName] AS ('User' + CAST(UserID AS VARCHAR)) PERSISTED

Answer 3

Select Coalesce(DisplayName, 'User' + Cast(UserID as varchar)) as UserName

Answer 4

I would be inclined to generate it before saving to the database. No input = make one up.

I also would not have user User1, User2, ... but user+random: user6238945, user9287561, user8934678, etc

If you use 1, 2, 3, 4 etc then you are exposing an internal sequence. If someone gets "user4" then I know other users 1 to 3 exist, as well as number 5. This exposure was used many years by AOL or Compuserve (?) for phishing attacks.