当.include中的相关对象为null时，Entityframework Core 2.0错误 [英] Entityframework Core 2.0 error when related object is null in .Include
本文介绍了当.include中的相关对象为null时，Entityframework Core 2.0错误的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在使用EF core 2.0和.Net core2.0开发我的webapi应用程序.
I am using EF core 2.0 and .Net core2.0 to develop my webapi application.
在以下查询中，当案件没有工作流(即可为空的工作流)时，我得到了例外.我得到的错误是"System.NullReferenceException:对象引用未设置为对象的实例."
In the following query, i am getting exception when the case doesnt have a workflow ie nullable workflow. the error i get is 'System.NullReferenceException: Object reference not set to an instance of an object.'
我怀疑c.workflow为null时.ThenInclude()上是否存在异常.
I doubt the exception is on the .ThenInclude() when the c.workflow is null.
案例实体:
public class Case
{
[Key]
public int CaseId { get; set; }
public int? WorkflowId { get; set; }
public Workflow Workflow { get; set; }
}
查询:
var item = await _context.Cases
.Include(c => c.CaseDetail)
.Include(c => c.Workflow).ThenInclude(wf => wf.CurrentWorkflowLevel)
.Include(c => c.Alerts)
.FirstOrDefaultAsync(c => c.CaseId == id);
考虑到工作流程为空，有人可以帮助实现此查询吗?
Can anyone help how to achieve this query considering the workflow is null?
例外:
System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler.IncludeLoadTreeNodeBase.<_AwaitMany>d__8.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler.<_IncludeAsync>d__18`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.TaskLiftingExpressionVisitor.<_ExecuteAsync>d__8`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.AsyncSelectEnumerable`2.AsyncSelectEnumerator.<MoveNext>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()
at System.Linq.AsyncEnumerable.SelectEnumerableAsyncIterator`2.<MoveNextCore>d__7.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()
at System.Linq.AsyncEnumerable.AsyncIterator`1.<MoveNext>d__10.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.<MoveNext>d__5.MoveNext()
Application Insights Telemetry (unconfigured): {"name":"Microsoft.ApplicationInsights.Dev.Exception","time":"2017-11-16T16:16:29.4502900Z","tags":{"ai.operation.id":"b6360c2b-4dabca2bb91d06ac","ai.application.ver":"1.0.0.0","ai.internal.nodeName":"UK2207793W1","ai.cloud.roleInstance":"UK2207793W1","ai.location.ip":"::1","ai.operation.name":"GET Cases/GetCases","ai.operation.parentId":"|b6360c2b-4dabca2bb91d06ac.","ai.internal.sdkVersion":"aspnet5c:2.1.1"},"data":{"baseType":"ExceptionData","baseData":{"ver":2,"properties":{"DeveloperMode":"true","Exception":"System.NullReferenceException: Object reference not set to an instance of an object.\r\n at Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler.IncludeLoadTreeNodeBase.<_AwaitMany>d__8.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler.<_IncludeAsync>d__18`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.TaskLiftingExpressionVisitor.<_ExecuteAsync>d__8`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.AsyncSelectEnumerable`2.AsyncSelectEnumerator.<MoveNext>d__3.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()\r\n at System.Linq.AsyncEnumerable.SelectEnumerableAsyncIterator`2.<MoveNextCore>d__7.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()\r\n at System.Linq.AsyncEnumerable.AsyncIterator`1.<MoveNext>d__10.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.<MoveNext>d__5.MoveNext()","AspNetCoreEnvironment":"Development","error":"System.NullReferenceException: Object reference not set to an instance of an object.\r\n at Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler.IncludeLoadTreeNodeBase.<_AwaitMany>d__8.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler.<_IncludeAsync>d__18`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.TaskLiftingExpressionVisitor.<_ExecuteAsync>d__8`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.AsyncSelectEnumerable`2.AsyncSelectEnumerator.<MoveNext>d__3.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()\r\n at System.Linq.AsyncEnumerable.SelectEnumerableAsyncIterator`2.<MoveNextCore>d__7.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()\r\n at System.Linq.AsyncEnumerable.AsyncIterator`1.<MoveNext>d__10.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.<MoveNext>d__5.MoveNext()","CategoryName":"Microsoft.EntityFrameworkCore.Query","contextType":"FDA.Operational.Core.Workflow.DBContext.WorkflowDBContext","{OriginalFormat}":"An exception occurred in the database while iterating the results of a query for context type '{contextType}'.{newline}{error}"},"exceptions":[{"id":22294293,"typeName":"System.NullReferenceException","message":"An exception occurred in the database while iterating the results of a query for context type 'FDA.Operational.Core.Workflow.DBContext.WorkflowDBContext'.\r\nSystem.NullReferenceException: Object reference not set to an instance of an object.\r\n at Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler.IncludeLoadTreeNodeBase.<_AwaitMany>d__8.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler.<_IncludeAsync>d__18`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.TaskLiftingExpressionVisitor.<_ExecuteAsync>d__8`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.AsyncSelectEnumerable`2.AsyncSelectEnumerator.<MoveNext>d__3.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()\r\n at System.Linq.AsyncEnumerable.SelectEnumerableAsyncIterator`2.<MoveNextCore>d__7.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()\r\n at System.Linq.AsyncEnumerable.AsyncIterator`1.<MoveNext>d__10.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.<MoveNext>d__5.MoveNext()","hasFullStack":true,"parsedStack":[{"level":0,"method":"Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler+IncludeLoadTreeNodeBase+<_AwaitMany>d__8.MoveNext","assembly":"Microsoft.EntityFrameworkCore, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60"},{"level":1,"method":"System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":2,"method":"System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":3,"method":"Microsoft.EntityFrameworkCore.Query.Internal.IncludeCompiler+<_IncludeAsync>d__18`1.MoveNext","assembly":"Microsoft.EntityFrameworkCore, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60"},{"level":4,"method":"System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":5,"method":"System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":6,"method":"System.Runtime.CompilerServices.TaskAwaiter`1.GetResult","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":7,"method":"Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.TaskLiftingExpressionVisitor+<_ExecuteAsync>d__8`1.MoveNext","assembly":"Microsoft.EntityFrameworkCore, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60"},{"level":8,"method":"System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":9,"method":"System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":10,"method":"Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor+AsyncSelectEnumerable`2+AsyncSelectEnumerator+<MoveNext>d__3.MoveNext","assembly":"Microsoft.EntityFrameworkCore, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60"},{"level":11,"method":"System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":12,"method":"System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":13,"method":"System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter.GetResult","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":14,"method":"System.Linq.AsyncEnumerable+SelectEnumerableAsyncIterator`2+<MoveNextCore>d__7.MoveNext","assembly":"System.Interactive.Async, Version=3.0.3000.0, Culture=neutral, PublicKeyToken=94bc3704cddfc263"},{"level":15,"method":"System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":16,"method":"System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":17,"method":"System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter.GetResult","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":18,"method":"System.Linq.AsyncEnumerable+AsyncIterator`1+<MoveNext>d__10.MoveNext","assembly":"System.Interactive.Async, Version=3.0.3000.0, Culture=neutral, PublicKeyToken=94bc3704cddfc263"},{"level":19,"method":"System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":20,"method":"System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":21,"method":"System.Runtime.CompilerServices.TaskAwaiter`1.GetResult","assembly":"System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e"},{"level":22,"method":"Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider+ExceptionInterceptor`1+EnumeratorExceptionInterceptor+<MoveNext>d__5.MoveNext","assembly":"Microsoft.EntityFrameworkCore, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60"}]}],"severityLevel":"Error"}}}
Exception thrown: 'System.NullReferenceException' in System.Private.CoreLib.dll
Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker:Information: Executed action FDA.Operational.Core.Workflow.WebAPI.Controllers.CasesController.GetCases (FDA.Operational.Core.Workflow.WebAPI) in 1562.4148ms
Application Insights Telemetry (unconfigured): {"name":"Microsoft.ApplicationInsights.Dev.Message","time":"2017-11-16T16:16:29.6814886Z","tags":{"ai.operation.id":"b6360c2b-4dabca2bb91d06ac","ai.application.ver":"1.0.0.0","ai.internal.nodeName":"UK2207793W1","ai.cloud.roleInstance":"UK2207793W1","ai.location.ip":"::1","ai.operation.name":"GET Cases/GetCases","ai.operation.parentId":"|b6360c2b-4dabca2bb91d06ac.","ai.internal.sdkVersion":"aspnet5c:2.1.1"},"data":{"baseType":"MessageData","baseData":{"ver":2,"message":"Executed action FDA.Operational.Core.Workflow.WebAPI.Controllers.CasesController.GetCases (FDA.Operational.Core.Workflow.WebAPI) in 1562.4148ms","severityLevel":"Information","properties":{"DeveloperMode":"true","ElapsedMilliseconds":"1562.4148","ActionName":"FDA.Operational.Core.Workflow.WebAPI.Controllers.CasesController.GetCases (FDA.Operational.Core.Workflow.WebAPI)","AspNetCoreEnvironment":"Development","CategoryName":"Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker","{OriginalFormat}":"Executed action {ActionName} in {ElapsedMilliseconds}ms"}}}}
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware:Error: An unhandled exception has occurred while executing the request
如果case.workflowid不为null，则查询工作正常.当它为null时发生异常，并且当它的前一个实体为null时在.ThenInclude()发生
The query works fine if case.workflowid is not null. Exception occurs when it is null and it happens at .ThenInclude() when its previous entity is null
目前，我正在尝试如下所示的方法.不确定这是正确的方法:
Currently i am trying somethign like below. Not sure it is the correct way:
var unassignedCases = await _context.Cases
.Include(c => c.CaseDetail)
.Include(c => c.Alerts)
.Where(c=>c.Workflow == null)
.ToListAsync();
var assignedCases = await _context.Cases
.Include(c => c.CaseDetail)
.Include(c => c.Workflow).ThenInclude(wf => wf.WorkflowRule)
.Include(c => c.Workflow).ThenInclude(wf => wf.CurrentWorkflowLevel).ThenInclude(wfl => wfl.FromRules)
.Include(c => c.Alerts)
.Where(c => c.Workflow != null)
.ToListAsync();
推荐答案
这是Core 2.0中的错误 已在beta/patch public 2.0.1中修复，您可以使用同步(不是异步解决方法)
This is a bug in core 2.0 Fixed in beta/patch public 2.0.1, you can use sync (not async as a work around)
修补程序public的路径: https://dotnet.myget.org/F/aspnet-2-0-2-october2017-patch-public/api/v3/index.json
Path to patch public: https://dotnet.myget.org/F/aspnet-2-0-2-october2017-patch-public/api/v3/index.json
这篇关于当.include中的相关对象为null时，Entityframework Core 2.0错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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