我有一个奇怪的问题,基本上我有以下代码:
var langauges = (from l in context.languages
where Model.LanguageIDs.Contains(l.LanguageID)
select l)
.ToList<language>();
我不知道为什么,但是我总是报错:
System.NullReferenceException:对象引用未设置为对象的实例
事情是它以前能工作,但是在那之后,我将所有应用程序都升级到了MVC5和EF6,它在此代码上开始崩溃。
虽然如果我检查
Model.Langauges
,它有几个ID,所以没关系。我还遍历了上下文,所有语言都有id。
我也这样写:
var langauges = (from l in context.languages
where 1==l.LanguageID
select l)
.ToList<language>();
而且这也起作用,所以我真的不明白,我做错了什么?
任何人都可以详细说明...?
堆栈跟踪:
at MySql.Data.Entity.SqlGenerator.Visit(DbPropertyExpression expression)
at MySql.Data.Entity.SqlGenerator.Visit(DbInExpression expression)
at System.Data.Entity.Core.Common.CommandTrees.DbInExpression.Accept[TResultType](DbExpressionVisitor`1 visitor)
at MySql.Data.Entity.SqlGenerator.VisitBinaryExpression(DbExpression left, DbExpression right, String op)
at MySql.Data.Entity.SqlGenerator.Visit(DbAndExpression expression)
at System.Data.Entity.Core.Common.CommandTrees.DbAndExpression.Accept[TResultType](DbExpressionVisitor`1 visitor)
at MySql.Data.Entity.SelectGenerator.Visit(DbFilterExpression expression)
at System.Data.Entity.Core.Common.CommandTrees.DbFilterExpression.Accept[TResultType](DbExpressionVisitor`1 visitor)
at MySql.Data.Entity.SqlGenerator.VisitInputExpression(DbExpression e, String name, TypeUsage type)
at MySql.Data.Entity.SelectGenerator.VisitInputExpressionEnsureSelect(DbExpression e, String name, TypeUsage type)
at MySql.Data.Entity.SelectGenerator.Visit(DbProjectExpression expression)
at System.Data.Entity.Core.Common.CommandTrees.DbProjectExpression.Accept[TResultType](DbExpressionVisitor`1 visitor)
at MySql.Data.Entity.SelectGenerator.GenerateSQL(DbCommandTree tree)
at MySql.Data.MySqlClient.MySqlProviderServices.CreateDbCommandDefinition(DbProviderManifest providerManifest, DbCommandTree commandTree)
at System.Data.Entity.Core.Common.DbProviderServices.CreateDbCommandDefinition(DbProviderManifest providerManifest, DbCommandTree commandTree, DbInterceptionContext interceptionContext)
at System.Data.Entity.Core.Common.DbProviderServices.CreateCommandDefinition(DbCommandTree commandTree, DbInterceptionContext interceptionContext)
at System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition..ctor(DbProviderFactory storeProviderFactory, DbCommandTree commandTree, DbInterceptionContext interceptionContext, IDbDependencyResolver resolver, BridgeDataReaderFactory bridgeDataReaderFactory, ColumnMapFactory columnMapFactory)
at System.Data.Entity.Core.EntityClient.Internal.EntityProviderServices.CreateCommandDefinition(DbProviderFactory storeProviderFactory, DbCommandTree commandTree, DbInterceptionContext interceptionContext, IDbDependencyResolver resolver)
at System.Data.Entity.Core.EntityClient.Internal.EntityProviderServices.CreateDbCommandDefinition(DbProviderManifest providerManifest, DbCommandTree commandTree, DbInterceptionContext interceptionContext)
at System.Data.Entity.Core.Common.DbProviderServices.CreateCommandDefinition(DbCommandTree commandTree, DbInterceptionContext interceptionContext)
at System.Data.Entity.Core.Objects.Internal.ObjectQueryExecutionPlanFactory.CreateCommandDefinition(ObjectContext context, DbQueryCommandTree tree)
at System.Data.Entity.Core.Objects.Internal.ObjectQueryExecutionPlanFactory.Prepare(ObjectContext context, DbQueryCommandTree tree, Type elementType, MergeOption mergeOption, Boolean streaming, Span span, IEnumerable`1 compiledQueryParameters, AliasGenerator aliasGenerator)
at System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)
at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClassb.<GetResults>b__a()
at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClassb.<GetResults>b__9()
at System.Data.Entity.Infrastructure.DefaultExecutionStrategy.Execute[TResult](Func`1 operation)
at System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
at System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0()
at System.Lazy`1.CreateValue()
at System.Lazy`1.LazyInitValue()
at System.Lazy`1.get_Value()
at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at MyProject.Infrastructure.DAL.Operations.UpdateUserinfo(Int32 id, Model Model) in :line 168
最佳答案
Model.LanguageIDs
是null
还是尚未设置您的context
?
另外,您是否允许在null
中的language
context.languages
条目?如果其中任何一个是null
,您将收到此异常。
关于c# - Int []。包含在EF6中不起作用,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/21028973/