MVC跟蹤字段，例如作者和編輯者（創建者和修改者）

Question

我正在尋找跟蹤數據庫中所有實體的“作者”和“編輯者”字段的最佳方法。

我首先創建一個基本模型，所有模型都繼承自該模型：

public class DatabaseEntity
{
    [Key]
    public int Id { get; set; }

    [Display(Name = "Last Modified By")]
    public ApplicationUser Editor { get; set; }

    [DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:MM/dd/yyyy}")]
    [Display(Name = "Last Modified")]
    public DateTime LastModified { get; set; }

    [Display(Name = "Created By")]
    public ApplicationUser Creator { get; set; }

    [DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:MM/dd/yyyy}")]
    public DateTime Created { get; set; }
}

這很好，但是我必須在控制器的每個動作中設置這些字段。 每次更新或編輯數據庫中的項目時，如何設置這些字段？ 我知道我可以在DbContext重寫Add ，但是我不知道如何從DbContext的HttpContext.Current.User.Identity獲取ApplicationUser 。 我努力了：

public class ApplicationDbContext : IdentityDbContext<ApplicationUser> {
    private readonly UserManager<ApplicationUser> userManager;
    private readonly HttpContext httpContext;

    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options, UserManager<ApplicationUser> userManager, IHttpContextAccessor contextAccessor)
    : base(options)
    {
        this.contextAccessor = contextAccessor;
        this.httpContext = contextAccessor.HttpContext;
        this.userManager = userManager;
    }

    public override EntityEntry<TEntity> Add<TEntity>(TEntity entity)
    {
        DatabaseEntity dbEntity = (entity as DatabaseEntity);
        if (dbEntity != null)
        {
            dbEntity.Created = DateTime.Now;
            dbEntity.Creator = await userManager.GetUserAsync(httpContext.User);
        }

        return base.Add(entity);
    }
}

但這會導致錯誤，因為userManager.GetUserAsync(httpContext.User); 需要await和public override EntityEntry<TEntity> Add<TEntity>(TEntity entity)不是異步的。

Answer 1

要獲取當前用戶，請勿使用UserManager<ApplicationUser> 。 帶注釋dbEntity.Creator = await userManager.GetUserAsync(httpContext.User); ，則會出現錯誤。檢測到類型為'CoreDb.Data.ApplicationDbContext'的服務的循環依賴關系。 由於您在ApplicationDbContext訪問UserManager<ApplicationUser> 。

我建議您嘗試通過使用當前用戶名查詢DbSet<ApplicationUser>來獲取當前用戶。

這是一個簡單的代碼：

    public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{       
    private readonly HttpContext httpContext;

    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options, IHttpContextAccessor contextAccessor)
        : base(options)
    {
        this.httpContext = contextAccessor.HttpContext;
    }       
    public DbSet<ApplicationUser> ApplicationUser { get; set; }
    public override EntityEntry<TEntity> Add<TEntity>(TEntity entity)
    {
        DatabaseEntity dbEntity = (entity as DatabaseEntity);
        var userName = httpContext.User.Identity.Name;
        if (dbEntity != null)
        {
            dbEntity.Created = DateTime.Now;
            dbEntity.Creator = userName == null ? null : ApplicationUser.Where(user => user.UserName == userName).FirstOrDefault();
        }
        return base.Add(entity);    
    }
    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);            
    }        
}