Why is this bad code?

Question

I was looking at a question on here about confessing your worst code ever written and I am not quite sure, because of my lack of knowledge on why this is bad code.

public string GetUsername (string userName)
{
    User user = DbLookup.GetUser(userName);
    return user.Username;
}

Is it because, it assumes username will exist and doesn't check for null? Or is there more to it?

https://stackoverflow.com/questions/130965/what-is-the-worst-code-youve-ever-written/191969#191969

Answer 1

because it returns the same thing that the user sends as input to the method... Username

Answer 2

It doesn't return the same string that was provided. It return the username from the database and the user may or may not exist - thus it could return null. The method name is perhaps incorrect given what it does. Someone in the original post mentioned that it should be CheckIfUsernameExistsAndReturn sorta method name.