我们重写SaveChangesAsync（）以自动为DateCreated，CreatedBy，LastDateModified和LastModifiedBy更新。使用CreatedBy和LastModifiedBt，我们需要标识用户的ID。
在ApplicationDbContext的构造函数中，我们添加了以下内容：
_userName = httpContextAccessor.HttpContext.User.Identity.Name;
//_userID = userManager.GetUserId(httpContext.HttpContext.User);
..并始终在此httpContextAccessor.HttpContext中获得null。有任何想法吗？我们在下面列出了源代码。
环境：
.NET Core 2.1
SQL Server
ApplicationDBContext.cs：
using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using AthlosifyWebArchery.Models;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Linq.Expressions;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Identity;
namespace AthlosifyWebArchery.Data
{
public class ApplicationDbContext : IdentityDbContext<ApplicationUser, ApplicationRole, string>
{
private readonly string _userID;
private readonly string _userName;
public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options,
IHttpContextAccessor httpContextAccessor
)
: base(options)
{
_userName = httpContextAccessor.HttpContext.User.Identity.Name;
//_userID = userManager.GetUserId(httpContext.HttpContext.User);
}
public DbSet<AthlosifyWebArchery.Models.TournamentBatchItem> TournamentBatchItem { get; set; }
public DbSet<AthlosifyWebArchery.Models.TournamentBatch> TournamentBatch { get; set; }
public virtual DbSet<AthlosifyWebArchery.Models.Host> Host { get; set; }
public DbSet<AthlosifyWebArchery.Models.HostApplicationUser> HostApplicationUser { get; set; }
protected override void OnModelCreating(ModelBuilder builder)
{
base.OnModelCreating(builder);
foreach (var entityType in builder.Model.GetEntityTypes())
{
// 1. Add the IsDeleted property
entityType.GetOrAddProperty("IsDeleted", typeof(bool));
// 2. Create the query filter
var parameter = Expression.Parameter(entityType.ClrType);
// EF.Property<bool>(post, "IsDeleted")
var propertyMethodInfo = typeof(EF).GetMethod("Property").MakeGenericMethod(typeof(bool));
var isDeletedProperty = Expression.Call(propertyMethodInfo, parameter, Expression.Constant("IsDeleted"));
// EF.Property<bool>(post, "IsDeleted") == false
BinaryExpression compareExpression = Expression.MakeBinary(ExpressionType.Equal, isDeletedProperty, Expression.Constant(false));
// post => EF.Property<bool>(post, "IsDeleted") == false
var lambda = Expression.Lambda(compareExpression, parameter);
builder.Entity(entityType.ClrType).HasQueryFilter(lambda);
}
// Many to Many relationship
builder.Entity<HostApplicationUser>()
.HasKey(bc => new { bc.HostID, bc.Id });
builder.Entity<HostApplicationUser>()
.HasOne(bc => bc.Host)
.WithMany(b => b.HostApplicationUsers)
.HasForeignKey(bc => bc.HostID);
builder.Entity<HostApplicationUser>()
.HasOne(bc => bc.ApplicationUser)
.WithMany(c => c.HostApplicationUsers)
.HasForeignKey(bc => bc.Id);
}
public override int SaveChanges(bool acceptAllChangesOnSuccess)
{
OnBeforeSaving();
return base.SaveChanges(acceptAllChangesOnSuccess);
}
public override Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = default(CancellationToken))
{
OnBeforeSaving();
return base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
}
private void OnBeforeSaving()
{
// Added
var added = ChangeTracker.Entries().Where(v => v.State == EntityState.Added && typeof(IBaseEntity).IsAssignableFrom(v.Entity.GetType())).ToList();
added.ForEach(entry =>
{
((IBaseEntity)entry.Entity).DateCreated = DateTime.UtcNow;
((IBaseEntity)entry.Entity).CreatedBy = _userID;
((IBaseEntity)entry.Entity).LastDateModified = DateTime.UtcNow;
((IBaseEntity)entry.Entity).LastModifiedBy = _userID;
});
// Modified
var modified = ChangeTracker.Entries().Where(v => v.State == EntityState.Modified &&
typeof(IBaseEntity).IsAssignableFrom(v.Entity.GetType())).ToList();
modified.ForEach(entry =>
{
((IBaseEntity)entry.Entity).LastDateModified = DateTime.UtcNow;
((IBaseEntity)entry.Entity).LastModifiedBy = _userID;
});
// Deleted
//var deleted = ChangeTracker.Entries().Where(v => v.State == EntityState.Deleted &&
//typeof(IBaseEntity).IsAssignableFrom(v.Entity.GetType())).ToList();
var deleted = ChangeTracker.Entries().Where(v => v.State == EntityState.Deleted).ToList();
deleted.ForEach(entry =>
{
((IBaseEntity)entry.Entity).DateDeleted = DateTime.UtcNow;
((IBaseEntity)entry.Entity).DeletedBy = _userID;
});
foreach (var entry in ChangeTracker.Entries()
.Where(e => e.State == EntityState.Deleted &&
e.Metadata.GetProperties().Any(x => x.Name == "IsDeleted")))
{
switch (entry.State)
{
case EntityState.Added:
entry.CurrentValues["IsDeleted"] = false;
break;
case EntityState.Deleted:
entry.State = EntityState.Modified;
entry.CurrentValues["IsDeleted"] = true;
break;
}
}
}
}
}
Startup.cs：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using AthlosifyWebArchery.Data;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using AthlosifyWebArchery.Models;
using DinkToPdf.Contracts;
using DinkToPdf;
namespace AthlosifyWebArchery
{
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
//services.AddHttpContextAccessor();
services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
services.AddSingleton(typeof(IConverter), new SynchronizedConverter(new PdfTools()));
services.Configure<CookiePolicyOptions>(options =>
{
// This lambda determines whether user consent for non-essential cookies is needed for a given request.
options.CheckConsentNeeded = context => true;
options.MinimumSameSitePolicy = SameSiteMode.None;
});
services.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(
Configuration.GetConnectionString("DefaultConnection")));
// Extended Application User from IdentityUser
// and ApplicationRole from IdentityRole
services.AddIdentity<ApplicationUser, ApplicationRole>(
options => options.Stores.MaxLengthForKeys = 128)
.AddEntityFrameworkStores<ApplicationDbContext>()
.AddDefaultUI()
.AddDefaultTokenProviders();
services.AddMvc()
.AddRazorPagesOptions(options =>
{
options.Conventions.AuthorizeFolder("/Tournaments");
options.Conventions.AuthorizeFolder("/TournamentAtheletes");
options.Conventions.AuthorizeFolder("/TournamentBatches");
options.Conventions.AuthorizeFolder("/TournamentContingents");
options.Conventions.AuthorizeFolder("/Admin");
//options.Conventions.AuthorizeFolder("/Private");
//options.Conventions.AllowAnonymousToPage("/Private/PublicPage");
//options.Conventions.AllowAnonymousToFolder("/Private/PublicPages");
})
.SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env,
ApplicationDbContext context,
RoleManager<ApplicationRole> roleManager,
UserManager<ApplicationUser> userManager)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
app.UseDatabaseErrorPage();
}
else
{
app.UseExceptionHandler("/Error");
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();
app.UseAuthentication();
app.UseMvc();
//UserManagerInitialData.Initialize(context, userManager, roleManager).Wait();
}
}
}
答案 0 :(得分：1)
HttpContext仅在请求期间有效。当.NET Core为ApplicationDbContext的调用创建Configure类时，没有有效的上下文。
您需要在IHttpContextAccessor构造函数中存储对DbContext的引用，然后可以使用该变量在HttpContext方法中访问OnBeforeSaving()属性。 / p>
例如：
public class ApplicationDbContext : IdentityDbContext<ApplicationUser, ApplicationRole, string>
{
private readonly IHttpContextAccessor _httpContextAccessor;
public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options,
IHttpContextAccessor httpContextAccessor
)
: base(options)
{
_httpContextAccessor = httpContextAccessor;
}
....
}
然后，在您的OnBeforeSaving（）方法中：
private void OnBeforeSaving()
{
var userName = _httpContextAccessor.HttpContext.User.Identity.Name;
...
}
将HttpContext视为电话。如果您在没有人打来电话的情况下拿起电话，则没有context，即为空。当有人打来电话时，您就有一个有效的context。这是网络电话的相同主体。 “启动”中的Configure方法不是网络调用，因此没有HttpContext。
从另一个站点：
HttpContext对象将保存有关当前http的信息 请求。详细而言，HttpContext对象将为 给予ASP.Net应用程序的每个请求以及此对象将 保留当前请求的特定信息，例如请求，响应， 服务器，会话，缓存，用户等。对于每个请求，一个新 将创建HttpContext对象，ASP.Net运行时将使用该对象 在请求处理期间。一个新的HttpContext对象将是 在请求开始时创建并在请求时销毁 完成。