如何使用 Net Core 在 DbContext 中获取用户信息

Question

我正在尝试开发一个类库，我想在其中实现自定义DbContext。在DbContext 的SaveChanges 方法中，我需要获取当前用户的信息（部门、用户名等）以进行审计。 DbContext 代码的一部分如下：

public override int SaveChanges()
{
    // find all changed entities which is ICreateAuditedEntity 
    var addedAuditedEntities = ChangeTracker.Entries<ICreateAuditedEntity>()
           .Where(p => p.State == EntityState.Added)
           .Select(p => p.Entity);

    var now = DateTime.Now;

    foreach (var added in addedAuditedEntities)
    {
        added.CreatedAt = now;
        added.CreatedBy = ?;
        added.CreatedByDepartment = ?
    }
    return base.SaveChanges();
}

想到两个选项：

• 使用HttpContext.Items保存用户信息，注入IHttpContextAccessor并从 HttpContext.Items(在这种情况下DbContext取决于HttpContext，是吗 对吗？）
• 使用 ThreadStatic 对象而不是 HttpContext.Items 并从对象中获取信息（我阅读了一些帖子 ThreadStatic 不安全）

问题：哪个最适合我的情况？您还有其他建议吗？

Answer 1

我实现了一种类似于this blog post 中介绍的方法，基本上涉及创建一个服务，该服务将使用依赖注入将HttpContext（和底层用户信息）注入特定上下文，或者您更喜欢使用它。

一个非常基本的实现可能如下所示：

public class UserResolverService  
{
    private readonly IHttpContextAccessor _context;
    public UserResolverService(IHttpContextAccessor context)
    {
        _context = context;
    }

    public string GetUser()
    {
       return _context.HttpContext.User?.Identity?.Name;
    }
}

您只需要在Startup.cs 文件中的ConfigureServices 方法中将其注入管道：

services.AddTransient<UserResolverService>();

最后，只需在您指定的 DbContext 的构造函数中访问它：

public partial class ExampleContext : IExampleContext
{
    private YourContext _context;
    private string _user;
    public ExampleContext(YourContext context, UserResolverService userService)
    {
        _context = context;
        _user = userService.GetUser();
    }
}

然后您应该能够使用_user 在您的上下文中引用当前用户。这可以很容易地扩展到存储/访问当前请求中可用的任何内容。

Answer 2

感谢@RionWilliams 的原始答案。这就是我们在.Net Core 3.1 中通过DbContext、AD B2C 用户和Web Api 解决CreatedBy 和UpdatedBy 的方法。 SysStartTime 和 SysEndTime 基本上是 CreatedDate 和 UpdatedDate，但通过临时表具有版本历史记录（有关任何时间点存储在表中的数据的信息）。

更多关于这里：

https://stackoverflow.com/a/64776658/3850405

通用接口：

public interface IEntity
{
    public DateTime SysStartTime { get; set; }

    public DateTime SysEndTime { get; set; }
    
    public int CreatedById { get; set; }
    
    public User CreatedBy { get; set; }

    public int UpdatedById { get; set; }

    public User UpdatedBy { get; set; }
}

数据库上下文：

public class ApplicationDbContext : DbContext
{
    public ApplicationDbContext(
        DbContextOptions options) : base(options)
    {
    }
    
    public DbSet<User> User { get; set; }

    public string _currentUserExternalId;
    
    public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        var user = await User.SingleAsync(x => x.ExternalId == _currentUserExternalId);

        AddCreatedByOrUpdatedBy(user);

        return (await base.SaveChangesAsync(true, cancellationToken));
    }

    public override int SaveChanges()
    {
        var user = User.Single(x => x.ExternalId == _currentUserExternalId);

        AddCreatedByOrUpdatedBy(user);

        return base.SaveChanges();
    }

    public void AddCreatedByOrUpdatedBy(User user)
    {
        foreach (var changedEntity in ChangeTracker.Entries())
        {
            if (changedEntity.Entity is IEntity entity)
            {
                switch (changedEntity.State)
                {
                    case EntityState.Added:
                        entity.CreatedBy = user;
                        entity.UpdatedBy = user;
                        break;
                    case EntityState.Modified:
                        Entry(entity).Reference(x => x.CreatedBy).IsModified = false;
                        entity.UpdatedBy = user;
                        break;
                }
            }
        }
    }
    
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        foreach (var property in modelBuilder.Model.GetEntityTypes()
            .SelectMany(t => t.GetProperties())
            .Where(p => p.ClrType == typeof(string)))
        {
            if (property.GetMaxLength() == null)
                property.SetMaxLength(256);
        }

        foreach (var property in modelBuilder.Model.GetEntityTypes()
            .SelectMany(t => t.GetProperties())
            .Where(p => p.ClrType == typeof(DateTime)))
        {
            property.SetColumnType("datetime2(0)");
        }

        foreach (var et in modelBuilder.Model.GetEntityTypes())
        {
            foreach (var prop in et.GetProperties())
            {
                if (prop.Name == "SysStartTime" || prop.Name == "SysEndTime")
                {
                    prop.ValueGenerated = Microsoft.EntityFrameworkCore.Metadata.ValueGenerated.OnAddOrUpdate;
                }
            }
        }

        modelBuilder.Entity<Question>()
            .HasOne(q => q.UpdatedBy)
            .WithMany()
            .OnDelete(DeleteBehavior.Restrict);
}

ExtendedApplicationDbContext：

public class ExtendedApplicationDbContext
{
    public ApplicationDbContext _context;
    public UserResolverService _userService;

    public ExtendedApplicationDbContext(ApplicationDbContext context, UserResolverService userService)
    {
        _context = context;
        _userService = userService;
        _context._currentUserExternalId = _userService.GetNameIdentifier();
    }
}

用户解析服务：

public class UserResolverService
{
    public readonly IHttpContextAccessor _context;

    public UserResolverService(IHttpContextAccessor context)
    {
        _context = context;
    }

    public string GetGivenName()
    {
        return _context.HttpContext.User.FindFirst(ClaimTypes.GivenName).Value;
    }

    public string GetSurname()
    {
        return _context.HttpContext.User.FindFirst(ClaimTypes.Surname).Value;
    }

    public string GetNameIdentifier()
    {
        return _context.HttpContext.User.FindFirst(ClaimTypes.NameIdentifier).Value;
    }

    public string GetEmails()
    {
        return _context.HttpContext.User.FindFirst("emails").Value;
    }
}

启动：

public void ConfigureServices(IServiceCollection services)
{
    services.AddHttpContextAccessor();
    
    services.AddTransient<UserResolverService>();
    
    services.AddTransient<ExtendedApplicationDbContext>();
    ...

然后可以像这样在任何Controller中使用：

public class QuestionsController : ControllerBase
{
    private readonly ILogger<QuestionsController> _logger;
    private readonly ExtendedApplicationDbContext _extendedApplicationDbContext;

    public QuestionsController(ILogger<QuestionsController> logger, ExtendedApplicationDbContext extendedApplicationDbContext)
    {
        _logger = logger;
        _extendedApplicationDbContext = extendedApplicationDbContext;
    }