.Net Core 2.1 - 无法访问已处置的对象。对象名称：'IServiceProvider'

Question

我刚刚将 .NET Core 2.0 迁移到 .NET Core 2.1。一切都很顺利，但是当我现在尝试登录时，出现以下错误：

• $exception {System.ObjectDisposedException：无法访问已处置的对象。 对象名称：“IServiceProvider”。

这发生在这段代码中：

public class AppContractResolver : DefaultContractResolver
{

    private readonly IServiceProvider _services;

    public AppContractResolver(IServiceProvider services)
    {
        _services = services;
    }

    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        var httpContextAccessor = _services.GetService<IHttpContextAccessor>();
        var user = httpContextAccessor.HttpContext.User;

        List<JsonProperty> properies = base.CreateProperties(type, memberSerialization).ToList();

        properies = FilterOneClaimGranted(type, properies, user);

        return properies;
    }

它发生在这一行：

var httpContextAccessor = _services.GetService<IHttpContextAccessor>();

这确实适用于 .NET Core 2.0

我尝试将HttpContextAccessor 添加到我的启动中，但没有成功。

那么，我该如何解决这个问题？

如果您需要更多代码，请告诉我。我很乐意提供更多，但我不知道您可能需要或不需要什么，因此我没有添加很多代码。'

编辑

我已将services.AddHttpContextAccessor(); 添加到我的创业公司，但这似乎不起作用。仍然收到错误。

编辑 2：

完整的堆栈跟踪：

- $exception    {System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'IServiceProvider'.
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ThrowHelper.ThrowObjectDisposedException()
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetService[T](IServiceProvider provider)
   at WebAPI.Extensions.AppContractResolver.CreateProperties(Type type, MemberSerialization memberSerialization) in C:\Users\luukw\Desktop\stage\blacky-api\Blacky\Extensions\Resolver\AppContractResolver.cs:line 25
   at Newtonsoft.Json.Serialization.DefaultContractResolver.CreateObjectContract(Type objectType)
   at Newtonsoft.Json.Serialization.DefaultContractResolver.CreateContract(Type objectType)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Newtonsoft.Json.Serialization.DefaultContractResolver.ResolveContract(Type type)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.GetContractSafe(Type type)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonSerializer.Deserialize(JsonReader reader, Type objectType)
   at Microsoft.AspNetCore.Mvc.Formatters.JsonInputFormatter.ReadRequestBodyAsync(InputFormatterContext context, Encoding encoding)}    System.ObjectDisposedException

Answer 1

在我的情况下，问题出现在Startup.cs

public void Configure(IApplicationBuilder app, IHostingEnvironment env, IServiceProvider services)
{
   var svc = services.GetService<IService>(); // <-- exception here
}

只需将services.GetService<>() 替换为app.ApplicationServices.GetService<>()

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
   var svc = app.ApplicationServices.GetService<IService>(); // no exception
}

希望对你有帮助

Answer 2

我建议不要打电话 services.GetService<IHttpContextAccessor>()，将IHttpContextAccessor注入构造函数，并使用私有字段存储值。

public AppContractResolver(IServiceProvider services, 
                           IHttpContextAccessor httpContextAccessor)
{
   _services = services;
   this.httpContextAccessor = httpContextAccessor;
}

还必须手动注册 HttpContextAccessor。 在 Startup.cs 的 RegisterServices 中添加，services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

Answer 3

如果您创建任何临时服务，例如 services.AddTransient...，那么 .net 核心将处置服务提供者。这是 .net core 2.2 的一个错误。

Answer 4

我遇到了这个错误，并且花了很长时间才解决，所以我将在此处发布。

这是引发错误的代码：

using var context = this.DbFactory.CreateDbContext();                
SqlParameter[] parameter =
{
    new SqlParameter("@ord_cust_id", ordCustId)
};
products = await context.GetProduct.FromSqlRaw<ProductEntity>($"{spName}  @ord_cust_id", parameter).AsNoTracking().ToListAsync();

抛出的异常在最后一行。这没有任何意义，因为上下文是由 DbFactory 创建的，因此不可能已经释放它。

找了好久，发现DbFactory的作用域是“Transient”所以改成Singleton，异常解决了。

这是启动时的代码：

 services.AddDbContextFactory<CDSEntities>(options =>
 {                
    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"));
 }, ServiceLifetime.Singleton); //changed to Singlton instead of Transient

Answer 5

对我来说，它适用于：

 public void ConfigureServices(IServiceCollection services)
{
  …
  services.AddHttpContextAccessor();
  …
}

然后：

     public void Configure(IApplicationBuilder app, IHttpContextAccessor accessor)
    {
    ...
    ...accessor.HttpContext.RequestService

     ...

    }

Answer 6

我在尝试在 Startup ➢ ConfigureServices 方法中获取服务时遇到了类似的异常：

public void ConfigureServices(IServiceCollection services)
{
    services.AddTransient<INotification>(provider =>
    {
        var hubContext = (IHubContext<NotificationHub>)provider
                  .GetService(typeof(IHubContext<NotificationHub>));

        // ↓↓↓ Exception: cannot access a disposed object. Object name: 'IServiceProvider'.
        var mediator = (IMediator)provider.GetService(typeof(IMediator)); 

        hubContext.SetListener(() =>  
            mediator.Send(new ...);
            ...
        });
    }
    ...
}
  

仅供参考：NotificationHub 是我实现自定义 INotificaiton 服务的自定义通知类。

---

通过创建本地范围服务解决了问题：

public void ConfigureServices(IServiceCollection services)
{
    services.AddTransient<INotification>(provider =>
    {
        var hubContext = (IHubContext<NotificationHub>)provider
                  .GetService(typeof(IHubContext<NotificationHub>));

          var myScope = provider.CreateScope(); // <<< creating a scoped sertvice
          var mediator = (IMediator)myScope.ServiceProvider.GetService(typeof(IMediator));

          hubContext.SetListener(() =>  
             mediator.Send(new ...);
             ...
        });
    }
    ...
}  

Answer 7

就我而言，调用者方法中缺少“await”运算符。

    public async Task<OrderResponse> CreateOrder(){
    //Do something
    var response = **await** CreateOrderItem();
    return response;
}

public async Task<ItemResponse> CreateOrderItem(){
    //Do something
}

CreateOrder() 中缺少“await”