首先是错误：
Cannot access a disposed object. A common cause of this error is disposing a context that was resolved from dependency injection and然后尝试在你的其他地方使用相同的上下文实例 应用。如果您正在调用Dispose（），则可能会发生这种情况 上下文，或将上下文包装在using语句中。如果你是 使用依赖注入，你应该让依赖注入 容器负责处理上下文实例。 对象名称：＆＃39; MemberContext＆＃39;。
我有3个项目，Domain，API和WebSPA应用。
Domain有2个模块，DomainModule和MediatorModule
public class DomainModule : Autofac.Module
{
protected override void Load(ContainerBuilder builder)
{
builder.RegisterAssemblyTypes(typeof(MemberContext).Assembly)
.AsImplementedInterfaces()
.InstancePerLifetimeScope(); // via assembly scan
builder.RegisterType<MemberContext>().AsSelf()
.InstancePerLifetimeScope(); // or individually
}
}
public class MediatorModule : Autofac.Module
{
protected override void Load(ContainerBuilder builder)
{
// enables contravariant Resolve() for interfaces with single contravariant ("in") arg
builder
.RegisterSource(new ContravariantRegistrationSource());
// mediator itself
builder
.RegisterType<Mediator>()
.As<IMediator>()
.InstancePerLifetimeScope();
// request handlers
builder
.Register<SingleInstanceFactory>(ctx =>
{
var c = ctx.Resolve<IComponentContext>();
return t =>
{
object o;
return c.TryResolve(t, out o) ? o : null;
};
})
.InstancePerLifetimeScope();
// notification handlers
builder
.Register<MultiInstanceFactory>(ctx =>
{
var c = ctx.Resolve<IComponentContext>();
return t => (IEnumerable<object>) c.Resolve(typeof(IEnumerable<>).MakeGenericType(t));
})
.InstancePerLifetimeScope();
}
}
在API项目中，我还有2个模块，ApplicationModule，以及与上面相同的MediatorModule。
public class ApplicationModule : Module
{
protected override void Load(ContainerBuilder builder)
{
builder.RegisterAssemblyTypes(typeof(Startup).Assembly)
.AsImplementedInterfaces()
.InstancePerLifetimeScope(); // via assembly scan
builder.RegisterType<MemberContext>().AsSelf().InstancePerLifetimeScope(); // or individually
}
}
不，当我调试时，我可以看到每个请求都会新建成员上下文，但是在第二次请求时，它会抛出错误。为了确保我不会发疯，我修改了dbcontext的构造函数来为上下文创建一个id，这样我就可以验证它们是不同的。我做错了什么？
public MemberContext(DbContextOptions<MemberContext> options) : base(options)
{
MemberContextId = Guid.NewGuid();
Console.WriteLine("member context created: " + MemberContextId);
}
这是API中的启动
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 IServiceProvider ConfigureServices(IServiceCollection services)
{
services.AddCors(options =>
{
options.AddPolicy("CorsPolicy",
builder => builder.AllowAnyOrigin()
.AllowAnyMethod()
.AllowAnyHeader()
// .AllowCredentials()
);
});
services.AddMvc()
.AddControllersAsServices();//Injecting Controllers themselves thru DI
//For further info see: http://docs.autofac.org/en/latest/integration/aspnetcore.html#controllers-as-services
AddSwaggerGen(services);
//var connection = Configuration["ConnectionString"];
//services.AddDbContext<MemberContext>(options => options.UseSqlServer(connection),ServiceLifetime.Scoped);
services.AddEntityFrameworkSqlServer()
.AddDbContext<MemberContext>(options =>
{
options.UseSqlServer(Configuration["ConnectionString"]
//,sqlServerOptionsAction: sqlOptions =>
//{
// sqlOptions.MigrationsAssembly(typeof(Startup).GetTypeInfo().Assembly.GetName().Name);
// sqlOptions.EnableRetryOnFailure(maxRetryCount: 10, maxRetryDelay: TimeSpan.FromSeconds(30), errorNumbersToAdd: null);
//}
);
},
ServiceLifetime.Scoped //Showing explicitly that the DbContext is shared across the HTTP request scope (graph of objects started in the HTTP request)
);
var container = new ContainerBuilder();
container.Populate(services);
container.RegisterAssemblyModules(typeof(VIN.Members.Domain.Entities.Member).Assembly,
typeof(Startup).Assembly);
return new AutofacServiceProvider(container.Build());
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
//NOTE: must be before UseMVC !!!
app.UseCors("CorsPolicy");
app.UseMvc();
app.UseSwagger();
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
});
}
private void AddSwaggerGen(IServiceCollection services)
{
services.AddSwaggerGen(options =>
{
options.DescribeAllEnumsAsStrings();
options.SwaggerDoc("v1", new Swashbuckle.AspNetCore.Swagger.Info
{
Title = "VIN Members HTTP API",
Version = "v1",
Description = "Members Service HTTP API",
TermsOfService = "Terms Of Service"
});
});
}
}
更新：
我要做的是删除一条记录。在客户端代码看起来像这样
onDelete(item: IMember) {
//TODO: replace this with dialog service component
if (window.confirm('Are sure you want to delete this member?')) {
//put your delete method logic here
this.service.deleteMember(item).subscribe(x => {
this.getMembers();
});
}
}
此删除请求将映射到将其传递给介体
的控制器控制器
// DELETE api/members/5
[HttpDelete("{id}")]
public void Delete(Guid id)
{
var command = new DeleteMember.Command(id);
_mediator.Send(command).ConfigureAwait(false);
}
最后处理程序
public class DeleteMember
{
public class Command : IRequest
{
public Command(Guid memberId)
{
Guard.NotNull(memberId, nameof(memberId));
MemberId = memberId;
}
public Guid MemberId { get; }
}
public class Handler : AsyncRequestHandler<Command>
{
private MemberContext _context;
public Handler(MemberContext context)
{
_context = context;
Console.WriteLine("Delete member context: " + context.MemberContextId);
}
protected override async Task HandleCore(Command cmd)
{
try
{
var member = await _context.FindAsync<Member>(cmd.MemberId);//.ConfigureAwait(false);
// if (member != null)
//// {
_context.Remove(member);
await _context.SaveChangesAsync().ConfigureAwait(false);
// }
}
catch (Exception e)
{
Console.WriteLine(e);
throw;
}
}
}
}
正如您所看到的，没有代码可以处理该上下文。抓我的头。
如果为null，请参阅此注释掉的成员检查。这也是抛出错误，我评论它只是为了看看会发生什么，现在它抛出SaveChangesAsync。
答案 0 :(得分：4)
请求完成后，上下文将被释放。由于命令处理程序使用SaveChangesAsync（），因此在保存完成之前会释放上下文。罪魁祸首是控制器方法:)。它也应该是异步的。
[HttpDelete("{id}")]
public async Task Delete(Guid id)
{
var command = new DeleteMember.Command(id);
await _mediator.Send(command).ConfigureAwait(false);
}
答案 1 :(得分：0)
您的DbContext是作用域的，这意味着每次在同一HTTP请求中请求一个DbContext对象时，依赖注入将返回相同的Dispose对象（在ASP.NET的情况下）。
这意味着您不应该在DbContext上调用using（否则同一个对象无法再次使用）。这似乎是你有意或无意发生的事情。
这意味着您不应该使用using。您是否在代码中的任何位置使用DbContext来对抗Dispose？
我不认为你展示了抛出异常的行。
更新的
尝试覆盖MemberContext课程中的public override void Dispose() {
base.Dispose();
}
。像这样：
ReactNative但只是在那里设置一个断点。当它中断时（如果它）检查堆栈跟踪并查看它的内容。
答案 2 :(得分：0)
根据我的经验，这也可能是由于在 WebAPI 中使用 async void 而不是 async Task 造成的。