System.ObjectDisposedException：本ObjectContext的实例已设置，不能再被用于需要连接的操作 [英] System.ObjectDisposedException: The ObjectContext instance has been disposed and can no longer be used for operations that require a connection

问题描述

我使用EF 4检索员工列表。

 公共ContentResult类型AutoCompleteResult（字符串SEARCHTEXT）
{
    清单＆LT;员工＆GT;清单= Employee.GetAllCurrentEmployees（）;
    清单＆LT;员工＆GT; filteredEmployees =名单
        。凡（X =方式＆gt;。x.GetName（）ToLower将（）包含（searchText.ToLower（）））
        .ToList（）;    的JavaScriptSerializer jsonSerializer =新的JavaScriptSerializer（）;
    变种jsonString = jsonSerializer.Serialize（filteredEmployees）的ToString（）;
    返回内容（jsonString）;
}
 

该列表检索确定，但是当我序列化，我得到这个例外;

  System.ObjectDisposedException：ObjectContext中实例已
 

  
  

布置，并且可以不再被用于
  需要连接的操作。
      生成：星期三，2010年11月17日16时06分56秒GMT

  System.ObjectDisposedException：ObjectContext中实例已
 

  
  

布置，并且可以不再被用于
  需要连接的操作。
  在
  System.Data.Objects.ObjectContext.EnsureConnection（）
  在
  System.Data.Objects.ObjectQuery 1.GetResults（可空 1
  forMergeOption）在
  System.Data.Objects.ObjectQuery 1.Execute（MergeOption
  mergeOption）在
  System.Data.Objects.DataClasses.EntityCollection 1.Load（名单 1
  收集，MergeOption mergeOption）结果
  在
  System.Data.Objects.DataClasses.EntityCollection 1.Load（MergeOption
  mergeOption）在
  System.Data.Objects.DataClasses.RelatedEnd.Load（）
  在
  System.Data.Objects.DataClasses.RelatedEnd.DeferredLoad（）
  在
  System.Data.Objects.DataClasses.EntityCollection<$c$c>1.System.Collections.IEnumerable.GetEnumerator()
  在
  System.Web.Script.Serialization.JavaScriptSerializer.SerializeEnumerable（IEnumerable的
  枚举，StringBuilder的某人，的Int32
  深度，Hashtable的objectsInUse，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal（对象
  0，StringBuilder的某人，深度Int，
  哈希表objectsInUse，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue（对象
  0，StringBuilder的某人，深度Int，
  哈希表objectsInUse，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.SerializeCustomObject（对象
  0，StringBuilder的某人，深度Int，
  哈希表objectsInUse，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal（对象
  0，StringBuilder的某人，深度Int，
  哈希表objectsInUse，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue（对象
  0，StringBuilder的某人，深度Int，
  哈希表objectsInUse，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.SerializeEnumerable（IEnumerable的
  枚举，StringBuilder的某人，的Int32
  深度，Hashtable的objectsInUse，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal（对象
  0，StringBuilder的某人，深度Int，
  哈希表objectsInUse，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue（对象
  0，StringBuilder的某人，深度Int，
  哈希表objectsInUse，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.Serialize（对象
  OBJ，StringBuilder的输出，
  SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.Serialize（对象
  OBJ，SerializationFormat
  serializationFormat）在
  System.Web.Script.Serialization.JavaScriptSerializer.Serialize（对象
  OBJ）在
  SHP.Controllers.EmployeeController.AutoCompleteResult（字符串
  SEARCHTEXT）在C：\\ Documents和
  设置\\ geoffreypayne \\我
  文档\\ Visual Studio中
  2010 \\项目\\ MVC \\ SHP \\ SHP \\ \\控制器EmployeeController.cs：行
  623在lambda_method（封闭，
  ControllerBase，对象[]）在
  System.Web.Mvc.ActionMethodDispatcher.Execute（ControllerBase
  控制器，对象[]参数）结果
  在
  System.Web.Mvc.ReflectedActionDescriptor.Execute（ControllerContext
  controllerContext，IDictionary的 2
  参数）在
  System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod（ControllerContext
  controllerContext，ActionDescriptor
  actionDescriptor，IDictionary的 2
  参数）在
  System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClassd.<InvokeActionMethodWithFilters>b__a()
  在
  System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter（IActionFilter
  过滤器，ActionExecutingContext
  preContext，Func键 1续）结果
  在
  System.Web.Mvc.ControllerActionInvoker＆LT;> C_的 DisplayClassd＆LT;> C 的_DisplayClassf.b__c（）
  在
  System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters（ControllerContext
  controllerContext，IList的 1的过滤器，
  ActionDescriptor actionDescriptor，
  IDictionary的 2参数）在
  System.Web.Mvc.ControllerActionInvoker.InvokeAction（ControllerContext
  controllerContext，字符串actionName）

我觉得这很奇怪。我已经获取员工的名单和DataContext的已被释放。所以，我为什么会得到这个错误？

解决方案

这听起来像你有没有尚未加载一些延迟加载的关系属性（其中有一个相关的N + 1的性能问题）。您可以尝试立即加载来看看这可以帮助;否则，明确装载数据列表中的每个项目，的前的关闭对象的上下文。

I am using EF 4 to retrieve a list of Employees.

public ContentResult AutoCompleteResult(string searchText)
{
    List<Employee> list = Employee.GetAllCurrentEmployees();
    List<Employee> filteredEmployees = list
        .Where(x => x.GetName().ToLower().Contains(searchText.ToLower()))
        .ToList();

    JavaScriptSerializer jsonSerializer = new JavaScriptSerializer();
    var jsonString = jsonSerializer.Serialize(filteredEmployees).ToString();
    return Content(jsonString);
}

The list is retrieved OK, but when I serialize it, I get this exception;

System.ObjectDisposedException: The ObjectContext instance has been

disposed and can no longer be used for operations that require a connection. Generated: Wed, 17 Nov 2010 16:06:56 GMT

System.ObjectDisposedException: The ObjectContext instance has been

disposed and can no longer be used for operations that require a connection. at System.Data.Objects.ObjectContext.EnsureConnection() at System.Data.Objects.ObjectQuery1.GetResults(Nullable1 forMergeOption) at System.Data.Objects.ObjectQuery1.Execute(MergeOption mergeOption) at System.Data.Objects.DataClasses.EntityCollection1.Load(List1 collection, MergeOption mergeOption)
at System.Data.Objects.DataClasses.EntityCollection1.Load(MergeOption mergeOption) at System.Data.Objects.DataClasses.RelatedEnd.Load() at System.Data.Objects.DataClasses.RelatedEnd.DeferredLoad() at System.Data.Objects.DataClasses.EntityCollection1.System.Collections.IEnumerable.GetEnumerator() at System.Web.Script.Serialization.JavaScriptSerializer.SerializeEnumerable(IEnumerable enumerable, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.SerializeCustomObject(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.SerializeEnumerable(IEnumerable enumerable, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.Serialize(Object obj, StringBuilder output, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.Serialize(Object obj, SerializationFormat serializationFormat) at System.Web.Script.Serialization.JavaScriptSerializer.Serialize(Object obj) at SHP.Controllers.EmployeeController.AutoCompleteResult(String searchText) in C:\Documents and Settings\geoffreypayne\My Documents\Visual Studio 2010\Projects\MVC\SHP\SHP\Controllers\EmployeeController.cs:line 623 at lambda_method(Closure , ControllerBase , Object[] ) at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClassd.<InvokeActionMethodWithFilters>b__a() at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func1 continuation)
at System.Web.Mvc.ControllerActionInvoker.<>c_DisplayClassd.<>c_DisplayClassf.b__c() at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList1 filters, ActionDescriptor actionDescriptor, IDictionary2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)

I find this very odd. I have already retrieved the list of employees and the DataContext has been disposed. So why would I get this error?

解决方案

It sounds like you have some lazily loaded relationship properties that have not yet loaded (which has an associated "n+1" performance concern). You can try eager loading to see if this helps; otherwise, explicitly load the data for each item in the list, before you close the object-context.

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