【发布时间】：2017-10-29 01:38:51
【问题描述】：
我正在 Microsoft Visual Studio Community 2017 中处理 ASP.NET 示例项目。我目前正在处理的项目昨天运行良好。今天打开项目，立马收到一个消息框：
项目系统遇到错误。
已存在具有相同键但不同值的元素。键：Microsoft.EntityFrameworkCore.InMemory
已写入诊断日志：
=====================
Crippling
System.AggregateException: One or more errors occurred. ---> System.ArgumentException: An element with the same key but a different value already exists. Key: Microsoft.EntityFrameworkCore.InMemory
at System.Collections.Immutable.ImmutableDictionary`2.HashBucket.Add(TKey key, TValue value, IEqualityComparer`1 keyOnlyComparer, IEqualityComparer`1 valueComparer, KeyCollisionBehavior behavior, OperationResult& result)
at System.Collections.Immutable.ImmutableDictionary`2.AddRange(IEnumerable`1 items, MutationInput origin, KeyCollisionBehavior collisionBehavior)
at System.Collections.Immutable.ImmutableDictionary`2.AddRange(IEnumerable`1 pairs, Boolean avoidToHashMap)
at System.Collections.Immutable.ImmutableDictionary`2.AddRange(IEnumerable`1 pairs)
at Microsoft.VisualStudio.ProjectSystem.Designers.ProjectBuildSubscriptionService.UpdateRuleSnapshotCore(IProjectVersionedValue`1 source, String ruleName, IRule rule, ImmutableDictionary`2 items, ImmutableDictionary`2 properties, ImmutableList`1 recentItemRenames, IProjectChangeDiff& diff)
at Microsoft.VisualStudio.ProjectSystem.Designers.ProjectRuleSubscriptionServiceBase`1.UpdateSnapshotCoreAsync(TSource source, IImmutableSet`1 subscribedElements, IProjectVersionedValue`1 previousResult)
at Microsoft.VisualStudio.ProjectSystem.Designers.CustomizableBlockSubscriberBase`3.<UpdateSnapshotAsync>d__28.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.ProjectSystem.Designers.CustomizableBlockSubscriberBase`3.<>c__DisplayClass27_0.<<Initialize>b__1>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Threading.JoinableTask.<JoinAsync>d__76.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Threading.JoinableTask`1.<JoinAsync>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.ProjectSystem.Designers.CustomizableBlockSubscriberBase`3.<<Initialize>b__27_0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.ProjectSystem.DataflowExtensions.<>c__DisplayClass23_0`2.<<CreateSelfFilteringTransformBlock>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Microsoft.VisualStudio.ProjectSystem.CommonProjectSystemTools.Rethrow(Exception ex)
at Microsoft.VisualStudio.ProjectSystem.ProjectErrorReporting.<>c__DisplayClass6_0.<SubmitErrorReport>b__0()
at Microsoft.VisualStudio.ProjectSystem.ExceptionFilter.<>c__DisplayClass2_0.<Guard>b__0()
at GuardMethodClass.GuardMethod(Func`1 , Func`2 , Func`2 )
--- End of inner exception stack trace ---
---> (Inner Exception #0) System.ArgumentException: An element with the same key but a different value already exists. Key: Microsoft.EntityFrameworkCore.InMemory
at System.Collections.Immutable.ImmutableDictionary`2.HashBucket.Add(TKey key, TValue value, IEqualityComparer`1 keyOnlyComparer, IEqualityComparer`1 valueComparer, KeyCollisionBehavior behavior, OperationResult& result)
at System.Collections.Immutable.ImmutableDictionary`2.AddRange(IEnumerable`1 items, MutationInput origin, KeyCollisionBehavior collisionBehavior)
at System.Collections.Immutable.ImmutableDictionary`2.AddRange(IEnumerable`1 pairs, Boolean avoidToHashMap)
at System.Collections.Immutable.ImmutableDictionary`2.AddRange(IEnumerable`1 pairs)
at Microsoft.VisualStudio.ProjectSystem.Designers.ProjectBuildSubscriptionService.UpdateRuleSnapshotCore(IProjectVersionedValue`1 source, String ruleName, IRule rule, ImmutableDictionary`2 items, ImmutableDictionary`2 properties, ImmutableList`1 recentItemRenames, IProjectChangeDiff& diff)
at Microsoft.VisualStudio.ProjectSystem.Designers.ProjectRuleSubscriptionServiceBase`1.UpdateSnapshotCoreAsync(TSource source, IImmutableSet`1 subscribedElements, IProjectVersionedValue`1 previousResult)
at Microsoft.VisualStudio.ProjectSystem.Designers.CustomizableBlockSubscriberBase`3.<UpdateSnapshotAsync>d__28.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.ProjectSystem.Designers.CustomizableBlockSubscriberBase`3.<>c__DisplayClass27_0.<<Initialize>b__1>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Threading.JoinableTask.<JoinAsync>d__76.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Threading.JoinableTask`1.<JoinAsync>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.ProjectSystem.Designers.CustomizableBlockSubscriberBase`3.<<Initialize>b__27_0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.ProjectSystem.DataflowExtensions.<>c__DisplayClass23_0`2.<<CreateSelfFilteringTransformBlock>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Microsoft.VisualStudio.ProjectSystem.CommonProjectSystemTools.Rethrow(Exception ex)
at Microsoft.VisualStudio.ProjectSystem.ProjectErrorReporting.<>c__DisplayClass6_0.<SubmitErrorReport>b__0()
at Microsoft.VisualStudio.ProjectSystem.ExceptionFilter.<>c__DisplayClass2_0.<Guard>b__0()
at GuardMethodClass.GuardMethod(Func`1 , Func`2 , Func`2 )<---
===================
它还导致了一些其他问题，例如我所有的 System 和 Microsoft 命名空间的 using 指令都出现错误：
可以找到类型或命名空间名称“System”（您是否缺少 using 指令或程序集引用？）
由于这些指令在其他项目中仍然可以正常工作，我怀疑当 EntityFramework 问题得到修复时它们会消退。
我已尝试重新启动 Visual Studio 和我的计算机，并尝试构建项目。我无法添加对该项目的引用。我收到消息框：
任务被取消
操作无法完成
对项目中命名空间的引用仍然可以正常工作。
感谢您的帮助。
【问题讨论】：
标签： asp.net visual-studio entity-framework entity-framework-core in-memory-database