ASP.NET 内核 Web API - 如何在 ApplicationDbContext 上的 SaveChangesAsync 中实现当前用户名

Question

In ASP.NET Core-6 Web API, I am implementing Entity Framework and ASP.NET Identity Db Context.

I have these services.

Interface:

public interface ICurrentUserService
{
    public string UserId { get; }
    public string UserName { get; }
}

Implementation:

public class CurrentUserService : ICurrentUserService
{
    public string UserId { get; }
    public string UserName { get; }

    public CurrentUserService(IHttpContextAccessor httpContextAccessor)
    {
        UserName = httpContextAccessor.HttpContext?.User?.FindFirstValue(ClaimTypes.Name);
        UserId = httpContextAccessor.HttpContext?.User?.FindFirstValue(ClaimTypes.NameIdentifier);
    }
}

Then I called it in ApplicationDbContext as shown below.

ApplicationDbContext:

public class ApplicationDbContext : IdentityDbContext<ApplicationUser, ApplicationRole, string, IdentityUserClaim<string>,ApplicationUserRole, IdentityUserLogin<string>,IdentityRoleClaim<string>, IdentityUserToken<string>>
{
    private readonly ICurrentUserService _currentUserService;
    private readonly IDateTime _dateTime;
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
    {
    }
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options,
        ICurrentUserService currentUserService, IDateTime dateTime)
        : base(options)
    {
        _currentUserService = currentUserService;
        _dateTime = dateTime;
    }
    public DbSet<ApplicationUser> ApplicationUsers { get; set; }
    public DbSet<ApplicationRole> ApplicationRoles { get; set; }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.ApplyConfigurationsFromAssembly(typeof(ApplicationDbContext).Assembly);
        base.OnModelCreating(builder);

        builder.ApplyConfiguration(new ApplicationUserConfigurations());
        builder.ApplyConfiguration(new ApplicationUserRoleConfigurations());
    }

    public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken = default)
    {
        foreach (var item in ChangeTracker.Entries<AuditableEntity>())
        {
            switch (item.State)
            {
                case EntityState.Modified:
                    item.Entity.LastModifiedBy = _currentUserService?.UserName;
                    item.Entity.LastModifiedAt = DateTime.Now;
                    break;

                case EntityState.Added:
                    item.Entity.CreatedBy = _currentUserService?.UserName;
                    item.Entity.CreatedAt = DateTime.Now;
                    break;

                case EntityState.Deleted:
                    item.Entity.DeletedBy = _currentUserService?.UserName;
                    item.Entity.DeletedAt = DateTime.Now;
                    item.Entity.IsDeleted = true;
                    break;

                default:
                    break;
            }
        }
        return await base.SaveChangesAsync(cancellationToken);
    }

    public override int SaveChanges()
    {
        OnBeforeSaveChanges(_currentUserService?.UserName);
        foreach (var item in ChangeTracker.Entries<AuditableEntity>())
        {
            switch (item.State)
            {
                case EntityState.Modified:
                    item.Entity.LastModifiedBy = _currentUserService?.UserName;
                    item.Entity.LastModifiedAt = DateTime.Now;
                    break;

                case EntityState.Added:
                    item.Entity.CreatedBy = _currentUserService?.UserName;
                    item.Entity.CreatedAt = DateTime.Now;
                    break;

                case EntityState.Deleted:
                    item.Entity.DeletedBy = _currentUserService?.UserName;
                    item.Entity.DeletedAt = DateTime.Now;
                    item.Entity.IsDeleted = true;
                    break;

                default:
                    break;
            }
        }
        return base.SaveChanges();
    }
}

UnitOfWork:

public class UnitOfWork : IUnitOfWork
{
    private readonly ApplicationDbContext _dbContext;

    public UnitOfWork(
        ApplicationDbContext dbContext,
        UserManager<ApplicationUser> userManager
        )
    {
        _dbContext = dbContext;
        _userManager = userManager;
    }

    public async Task Save()
    {
        await _dbContext.SaveChangesAsync();
    }
}

In the application, when I implement it as:

 await _unitOfWork.Employees.InsertAsync(bankUser);
 await _unitOfWork.Save();

I expected it to also insert UserName in the CreatedBy field, but it is null.

But If I implement it directly as:

_currentUserService.UserName

inside the application, it works..

What could be wrong and how do I correct this?

Thanks

Answer 1

I think the problem is that you assign UserName and UserId right away when the service is constructed. At the time of the construction of your service there might not be a HttpContext to work with.

Try using the HttpContextAccessor in your getter like this:

public class CurrentUserService : ICurrentUserService
{
    private readonly IHttpContextAccessor httpContextAccessor;

    public CurrentUserService(IHttpContextAccessor httpContextAccessor)
    {
        this.httpContextAccessor = httpContextAccessor;
    }

    public string UserName => this.httpContextAccessor.HttpContext?.User?.Identity?.Name;

    public string UserId => this.httpContextAccessor.HttpContext?.User?.Claims?.FirstOrDefault(c => c.Type == System.Security.Claims.ClaimTypes.NameIdentifier)?.Value;
}

By using the HttpContextAccessor when the property is accessed you make sure to get the currently valid one (if there is any).