i have a problem using Contains()
method with parameter coming from the method arguments.
i am using entity framework core 1.1 and mysql connector version 6.10.0-alpha.
i have this code:
public IEnumerable<Message> search(string content) {
var bla = this.appDbContext.Messages.Where(x => x.Content.Contains("edit")).ToList();
var bla1 = this.appDbContext.Messages.Where(x => x.Content=="edit").ToList();
var bla2 = this.appDbContext.Messages.Where(x => x.Content==content).ToList();
var bla3 = this.appDbContext.Messages.Where(x => x.Content.Contains(content)).ToList();
...
the first 3 lines works,
however, the fourth line (bla3) returns the following error:
fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[0] An unhandled exception has occurred while executing the request System.InvalidOperationException: When called from 'VisitChildren', rewriting a node of type 'System.Linq.Expressions.Expression' must return a non-null value of the same type. Alternatively, override 'VisitChildren' and change it to not visit children of this type.
at System.Linq.Expressions.ExpressionVisitor.VisitAndConvert[T](ReadOnlyCollection'1 nodes, String callerName) at Microsoft.EntityFrameworkCore.Query.Expressions.SqlFunctionExpression.VisitChildren(ExpressionVisitor visitor) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.ExpressionVisitorBase.VisitExtension(Expression node) at Microsoft.EntityFrameworkCore.Query.Expressions.SqlFunctionExpression.Accept(ExpressionVisitor visitor) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.ConditionalRemovingExpressionVisitor.Visit(Expression node) at Microsoft.EntityFrameworkCore.Query.Expressions.LikeExpression.VisitChildren(ExpressionVisitor visitor) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.ExpressionVisitorBase.VisitExtension(Expression node) at Microsoft.EntityFrameworkCore.Query.Expressions.LikeExpression.Accept(ExpressionVisitor visitor) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.ConditionalRemovingExpressionVisitor.Visit(Expression node) at Microsoft.EntityFrameworkCore.Query.RelationalQueryModelVisitor.VisitWhereClause(WhereClause whereClause, QueryModel queryModel, Int32 index) at Remotion.Linq.QueryModelVisitorBase.VisitBodyClauses(ObservableCollection'1 bodyClauses, QueryModel queryModel) at Remotion.Linq.QueryModelVisitorBase.VisitQueryModel(QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.VisitQueryModel(QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.RelationalQueryModelVisitor.VisitQueryModel(QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.CreateQueryExecutor[TResult](QueryModel queryModel) --- End of stack trace from previous location where exception was thrown ---
why can't i use parameter from the method arguments inside Contains()
linq expression?
and what can i do to be able to use it?
bug officially fixed in version 6.10.1: https://www.nuget.org/packages/MySql.Data/6.10.1-beta
https://bugs.mysql.com/bug.php?id=84505
[9 Feb 21:17] Christine Cole
Posted by developer:
Fixed as of the upcoming MySQL Connector/NET 6.10.1 release, and here's the changelog entry:
EF Core: Using the Contains method in an expression with a variable generated an exception.
Thank you for the bug report.
and here is the official release post:
http://insidemysql.com/mysql-connectornet-6-10-1-beta-has-been-released/
Bugs Fixed
- EF Core: Using the Contains method in an expression with a variable generated an exception. (Bug #25394204, Bug #84505)
apparently this is a real bug and not something i missunderstand in the way entity framework works.
we started talking about it here in entity framework's github issues board:
Wrong query generation when using Contains inside where predicate. #6687 https://github.com/aspnet/EntityFramework/issues/6687#issuecomment-272543460
and then it was branched over to mysql bugs forum:
Bug #84505 Using Contains method in expression with a variable throws exception in EF Core http://bugs.mysql.com/bug.php?id=84505
and to a new dedicated issue in entity framework's github issues board:
Query : possible error around conditional removing visitor and sql functions #7441 https://github.com/aspnet/EntityFramework/issues/7441
hope this is fixed soon.