case insensitive string filter

[rpimentaf]

Hi, everone!!!
I've implemented the @PascalSenn solutution "Filtering.Demo" but in one specific case i'm facing an error like this:
"message": "Object reference not set to an instance of an object.", "stackTrace": " at lambda_method1333(Closure , IAerodromoDTOModel ) at System.Linq.Enumerable.WhereEnumerableIterator1.MoveNext()
at System.Linq.Enumerable.EnumerablePartition1.MoveNext() at HotChocolate.Types.Pagination.QueryableCursorPagination1.<>c__DisplayClass6_0.b__0()
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.Tasks.Task.<>c.<.cctor>b__277_0(Object obj)
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
--- End of stack trace from previous location ---
at HotChocolate.Types.Pagination.QueryableCursorPagination1.ExecuteAsync(IQueryable1 query, Int32 offset, CancellationToken cancellationToken)
at HotChocolate.Types.Pagination.CursorPaginationAlgorithm2.ApplyPaginationAsync(TQuery query, CursorPagingArguments arguments, Nullable1 totalCount, CancellationToken cancellationToken)
at HotChocolate.Types.Pagination.QueryableCursorPagingHandler1.ResolveAsync(IResolverContext context, IQueryable1 source, CursorPagingArguments arguments, CancellationToken cancellationToken)
at HotChocolate.Types.Pagination.CursorPagingHandler.HotChocolate.Types.Pagination.IPagingHandler.SliceAsync(IResolverContext context, Object source)
at HotChocolate.Types.Pagination.PagingMiddleware.InvokeAsync(IMiddlewareContext context)
at HotChocolate.Utilities.MiddlewareCompiler1.ExpressionHelper.AwaitTaskHelper(Task task) at HotChocolate.Execution.Processing.Tasks.ResolverTask.ExecuteResolverPipelineAsync(CancellationToken cancellationToken) at HotChocolate.Execution.Processing.Tasks.ResolverTask.TryExecuteAsync(CancellationToken cancellationToken)"

My FilterConvention:
public class CustomFilteringConvention : FilterConvention { protected override void Configure(IFilterConventionDescriptor descriptor) { descriptor.AddDefaults(); descriptor.Operation(DefaultFilterOperations.Contains).Name("contains"); descriptor.AddProviderExtension( new QueryableFilterProviderExtension( x => x.AddFieldHandler<QueryableStringInvariantContainsHandler>())); descriptor.Operation(DefaultFilterOperations.Equals).Name("equals"); descriptor.AddProviderExtension( new QueryableFilterProviderExtension( x => x.AddFieldHandler<QueryableStringInvariantEqualsHandler>())); } }

And my QueryableStringInvariantContainsHandler is:
public class QueryableStringInvariantContainsHandler : QueryableStringOperationHandler { private static readonly MethodInfo _toLower = typeof(string) .GetMethods() .Single( x => x.Name == nameof(string.ToLower) && x.GetParameters().Length == 0); public QueryableStringInvariantContainsHandler(InputParser inputParser) : base(inputParser) { } protected override int Operation => DefaultFilterOperations.Contains; public override Expression HandleOperation( QueryableFilterContext context, IFilterOperationField field, IValueNode value, object parsedValue) { Expression property = context.GetInstance(); if (parsedValue is string str) { MethodInfo contains = typeof(string).GetMethods().Where(x => x.Name == "Contains").First(); var result = Expression.Call( Expression.Call(property, _toLower), contains, Expression.Constant(str.ToLower())); return result; } throw new InvalidOperationException(); } }

Does anyone know why this error is hapening? Is it because of null values in returned from the API?

Tks very much!!!!