Extending Filtering

[rpimentaf]

HI, everyone!!!
As documented here (https://chillicream.com/docs/hotchocolate/api-reference/extending-filtering#extending-iqueryable), I'm trying to implement a case insensitive funcionality. Besides the result of the QueryableStringInvariantEqualsHandler seems to be correct, the server returns the following error : "Object reference not set to an instance of an object.".
The stack trace showed is:

"   at lambda_method1339(Closure , MyDTOModel )
   at System.Linq.Enumerable.WhereListIterator`1.MoveNext()
   at System.Linq.Enumerable.EnumerablePartition`1.MoveNext()
   at HotChocolate.Types.Pagination.QueryableOffsetPagination`1.<>c__DisplayClass6_0.<ExecuteAsync>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.QueryableOffsetPagination`1.ExecuteAsync(IQueryable`1 query, CancellationToken cancellationToken)
   at HotChocolate.Types.Pagination.OffsetPaginationAlgorithm`2.ApplyPaginationAsync(TQuery query, OffsetPagingArguments arguments, Nullable`1 totalCount, CancellationToken cancellationToken)
   at HotChocolate.Types.Pagination.QueryableOffsetPagingHandler`1.ResolveAsync(IResolverContext context, IQueryable`1 source, OffsetPagingArguments arguments, CancellationToken cancellationToken)
   at HotChocolate.Types.Pagination.OffsetPagingHandler.HotChocolate.Types.Pagination.IPagingHandler.SliceAsync(IResolverContext context, Object source)
   at HotChocolate.Types.Pagination.PagingMiddleware.InvokeAsync(IMiddlewareContext context)
   at HotChocolate.Utilities.MiddlewareCompiler`1.ExpressionHelper.AwaitTaskHelper(Task task)
   at HotChocolate.Execution.Processing.Tasks.ResolverTask.ExecuteResolverPipelineAsync(CancellationToken cancellationToken)
   at HotChocolate.Execution.Processing.Tasks.ResolverTask.TryExecuteAsync(CancellationToken cancellationToken)"

Does anyone know what is wrong?
Thanks!!!! (editado)

[aaron-manning]

Here's what i'm using for a case-insensitive contains and not contains filter.

Hoping it might help you with your issue as it works fine for me, nulls or no.

/// <summary>
/// Configure 'contains' gql string operation to be case insensitive
/// </summary>
public class QueryableStringInvariantContainsHandler : QueryableStringOperationHandler
{
    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 null)
        {
            return Expression.Equal(property, Expression.Constant(null));
        }

        if (parsedValue is string str)
        {
#pragma warning disable CS8604 // Possible null reference argument.
            var toLower = Expression.Call(property, typeof(string).GetMethod("ToLower", Type.EmptyTypes));
            return Expression.Call(
                toLower,
                typeof(string).GetMethod(nameof(string.Contains), new Type[] { typeof(string) }),
                Expression.Constant(str.ToLower())
            );
#pragma warning restore CS8604 // Possible null reference argument.
        }
        throw new InvalidOperationException();
    }
}

/// <summary>
/// Configure 'ncontains' gql string operation to be case insensitive
/// Inherits from the 'contains' implementation and negates the output
/// </summary>
public class QueryableStringInvariantNotContainsHandler : QueryableStringInvariantContainsHandler
{
    public QueryableStringInvariantNotContainsHandler(InputParser inputParser) : base(inputParser) { }

    protected override int Operation => DefaultFilterOperations.NotContains;

    public override Expression HandleOperation(
        QueryableFilterContext context,
        IFilterOperationField field,
        IValueNode value,
        object? parsedValue
    )
    {
        // inclusive nulls
        // var property = context.GetInstance();
        // return Expression.Or(Expression.Equal(property, Expression.Constant(null)), Expression.Not(base.HandleOperation(context, field, value, parsedValue)));

        // exclusive nulls
        return Expression.Not(base.HandleOperation(context, field, value, parsedValue));
    }
}

Perhaps paste your code and a snippet of the schema and query?