无法访问已处置的对象 - wcf 客户端

Question

我有一个遇到问题的 WCF 客户端。
我不时收到此异常：Cannot access a disposed object。这就是我打开连接的方式：

private static LeverateCrmServiceClient crm = null;

public static CrmServiceClient Get(string crmCertificateName)
        {

            if (crm != null)
            {
                crm.Close();
            }
            try 
            {
                crm = new LeverateCrmServiceClient("CrmServiceEndpoint");
                crm.ClientCredentials.ClientCertificate.SetCertificate(
                               StoreLocation.LocalMachine,
                               StoreName.My,
                               X509FindType.FindBySubjectName,
                               crmCertificateName);
            }
            catch (Exception e) 
            {
                log.Error("Cannot access CRM ", e);
                throw;
            }
            return crm;
        }

如您所见，我每次都在关闭并重新打开连接。 你认为可能是什么问题？

堆栈：

System.ServiceModel.Security.MessageSecurityException: Message security verification failed. ---> System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'System.ServiceModel.Security.SymmetricSecurityProtocol'.
  at System.ServiceModel.Channels.CommunicationObject.ThrowIfClosedOrNotOpen()
  at System.ServiceModel.Security.MessageSecurityProtocol.VerifyIncomingMessage(Message& message, TimeSpan timeout, SecurityProtocolCorrelationState[] correlationStates)
  --- End of inner exception stack trace ---

Server stack trace:
  at System.ServiceModel.Security.MessageSecurityProtocol.VerifyIncomingMessage(Message& message, TimeSpan timeout, SecurityProtocolCorrelationState[] correlationStates)
  at System.ServiceModel.Channels.SecurityChannelFactory`1.SecurityRequestChannel.ProcessReply(Message reply, SecurityProtocolCorrelationState correlationState, TimeSpan timeout)
  at System.ServiceModel.Channels.SecurityChannelFactory`1.SecurityRequestChannel.Request(Message message, TimeSpan timeout)
  at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
  at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
  at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

Exception rethrown at [0]:
  at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
  at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
  at Externals.CrmService.ICrmService.GetTradingPlatformAccountDetails(Guid ownerUserId, String organizationName, String businessUnitName, Guid tradingPlatformAccountId)
  at MyAppName.Models.ActionsMetadata.Trader.BuildTrader(Guid tradingPlatformAccountId) in C:\Users\X\Documents\Visual Studio 2010\Projects\MyAppName\MyAppName\Models\ActionsMetadata\Trader.cs:line 120
  at MyAppName.Models.ActionsMetadata.Trader.Login(String accountNumber, String password) in C:\Users\X\Documents\Visual Studio 2010\Projects\MyAppName\MyAppName\Models\ActionsMetadata\Trader.cs:line 48
  at MyAppName.Models.ActionsMetadata.Handlers.LoginHandler.Handle(StepHandlerWrapper wrapper) in C:\Users\X\Documents\Visual Studio 2010\Projects\MyAppName\MyAppName\Models\ActionsMetadata\Handlers\LoginHandler.cs:line 23
  at MyAppName.Models.ActionsMetadata.Handlers.HandlerInvoker.Invoke(IAction brokerAction, ActionStep actionStep, Dictionary`2 stepValues, HttpContext httpContext, BaseStepDataModel model) in C:\Users\X\Documents\Visual Studio 2010\Projects\MyAppName\MyAppName\Models\ActionsMetadata\Handlers\StepServerInoker.cs:line 42
  at MyAppName.Controllers.LoginController.Login(String step) in C:\Users\X\Documents\Visual Studio 2010\Projects\MyAppName\MyAppName\Controllers\LoginController.cs:line 35
  at lambda_method(Closure , ControllerBase , Object[] )
  at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
  at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
  at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass15.<InvokeActionMethodWithFilters>b__12()
  at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
  at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
  at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)

Answer 1

根据该堆栈跟踪，我假设您有一个 ASP.NET MVC 应用程序，其中包含一些调用 Get 方法以获取 CrmServiceClient 对象的代码，然后继续调用该 CrmServiceClient 对象上的各种方法。例如，登录过程的一部分就是这样做的。

您的Get 方法的工作方式是，每次调用它时，它都会首先关闭它之前返回的CrmServiceClient 对象（无论它是否仍在使用）然后创建并返回一个新的一个。

想象一下，两个用户几乎同时尝试登录到您的应用程序 - 彼此相差几毫秒。处理第一个用户登录的线程调用Get 并获取其CrmServiceClient 对象，然后一毫秒后处理第二个用户登录的线程调用Get，这导致第一个线程的CrmServiceClient 对象被关闭。但是，第一个线程仍在运行，现在当它尝试调用它的 CrmServiceClient 对象上的方法时，它会得到一个 System.ObjectDisposedException: Cannot access a disposed object。

“如您所见，我每次都在关闭和重新打开连接。”

Get 方法中当前的代码不是实现此目标的好方法。相反，您应该让调用者有责任关闭（或处置）CrmServiceClient 对象，并且您可能应该将您的 Get 方法重命名为 Open 或 Create 来建议这一点。调用者应使用using 语句来确保对象已关闭/处置，无论发生任何异常：

using (CrmServiceClient client = CrmServiceFactory.Get("my-crm-certificate"))
{
    client.Something();
    client.GetTradingPlatformAccountDetails();
    client.SomethingElse();
} // client is automatically closed at the end of the 'using' block