ASP.NET Core 2：UserManager与DbContext

Question

I'm using the generic IdentityUser<T> class for my user model and with using string as primary key everything works fine, but I would like to use long as key type. So, I'm using the generic version of IdentityUser. Now I discovered that the UserManager has the following definition:

public class UserManager<TUser> : IDisposable where TUser : class

and the following function

public virtual Task<TUser> FindByIdAsync(string userId);

It seems that this doesn't fit together because the function requires a string as key/ID. TUser must be TUser<TKey> .

The question is now if there is any performance loss because of parsing string to long (of course there is) or is it better to get the user object direct from DbContext with a normal database select? Does the UserManager has any benefits so that it would be recommended to use it even with the string key requirement?

Thanks!

Answer 1

You can setup your User table to use a different type for a primary key by extending the IdentityUser class like so:

public class MyUser : IdentityUser<long>

And then injecting UserManager<MyUser> into your classes to manage them.

https://docs.microsoft.com/en-us/aspnet/core/security/authentication/identity-primary-key-configuration?tabs=aspnetcore2x

Answer 2

FindByIdAsync always takes string because it is a common denominator of every class. Instead of polluting with generics all over the place (like in Identity v2) you will have to convert your digits to string and pass it on. On DB side it is handled by EF anyway for you.

You can have your own UserManager class that inherits from UserManager and have a method override FindByIdAsync(long id) that just does id.ToString()

    public virtual Task<TUser> FindByIdAsync(long userId)
    {
         return base.FindByIdAsync(userId.ToString());
    }

Answer 3

From this link you can see that it is possible to change type of the key. Initially it is set to string, so that you can use values like int or guid out of the box.

Code taken from mentioned link. Firstly change your user to desired key type:

 public class ApplicationUser : IdentityUser<long>
 {
 }

Edit Application Role class:

public class ApplicationRole : IdentityRole<long>
{
} 

In application context class, add your new key:

public class ApplicationDbContext : IdentityDbContext<ApplicationUser, ApplicationRole, long>