Question

我正在尝试开发一个类库，我希望在其中实现自定义DbContext。在SaveChanges的{{1}}方法中，我需要获取当前用户的信息（部门，用户名等）以供审核。 DbContext代码的某些部分位于以下位置：

DbContext

有两种选择：

使用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(); }保存用户信息，注入IHttpContextAccessor并从中获取信息 HttpContext.Items（在这种情况下，HttpContext.Items取决于DbContext，是吗？正确的吗？）
使用ThreadStatic对象代替HttpContext并从对象获取信息（我阅读了一些帖子那个ThreadStatic不安全）

问题：哪种情况最适合我的情况？你有其他建议吗？

Answer 1

我实现了类似于this blog post中涵盖的方法，并且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，或者但你更愿意使用它。

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ConfigureServices文件的Startup.cs方法中将其注入管道：

services.AddTransient<UserResolverService>();

最后，只需在指定的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，您应该可以使用_user来引用上下文中的当前用户。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提供原始答案。这是我们通过DbContext 3.1中的AD B2C，.Net Core用户和Web Api解决CreatedBy和UpdatedBy的方式。 SysStartTime和SysEndTime基本上是CreatedDate和UpdatedDate，但通过时态表具有版本历史记录（有关在任何时间点存储在表中的数据的信息）。

有关此内容的更多信息：

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; }
}

DbContext：

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();
    }
}

UserResolverService：

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>();
    ...

然后可以在任何Controller中这样使用：

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

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

如何使用Net Core在DbContext中获取用户信息

2 个答案: