Geek Answers Handbook

Int []. Contains not working in EF6

I have a weird problem, basically I have this code:

var langauges = (from l in context.languages where Model.LanguageIDs.Contains(l.LanguageID) select l) .ToList<language>();

I don’t know why, but I always get the error message:

System.NullReferenceException: object reference not set to object instance

The fact is that it worked before that, but after that I updated my entire application to MVC5 and EF6, it started to crash in this code.

Although, if I check Model.Langauges , it has several identifiers, so this is normal.

I also went in cycles in a high context. Language and they all have identifiers.

I also wrote like this:

 var langauges = (from l in context.languages where 1==l.LanguageID select l) .ToList<language>();

And this also works, so I really don’t understand what am I doing wrong?

Anyone can work out ...?

Stacktrace:

  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
+3
c # linq entity-framework
source share
2 answers

Is it possible that Model.LanguageIDs null or your context is not set yet?

Also, do you allow null language entries in context.languages ? If any of them is null , you will get this exception.

0
source share

Ok, I ran into the same problem, but found a solution that might help you.

In my case, the LanguageID identifier collection type was List<long> (unisgned int in the database), and LanguageID was int . And this type difference caused a problem.

I know this is still a mistake, and from a .net point of view this is absolutely correct, but I hope that my post will help someone

0
source share

More articles:


All Articles