Adding a filter on a row which contains null data causes a null reference exception

[riccardorestagno]

Version

2.8.4

Details

When adding a filter on a string which contains null data, GridifyQueryable throws a null reference exception. Here is an example of the crash:

public PersonQueryResult<PersonUIModel> RunGetPerson(string Id, PagingRequest pagingRequest)
    {
        IEnumerable<PersonUIModel> persons= _context.Person
           .Where(ct => ct.Id== Id)
           .AsEnumerable()
           .Select(ct => new PersonUIModel
           {
               Id = ct.Id,
               FirstName = ct.FirstName,
               LastName = ct.LastName,
           });

        QueryablePaging<PersonUIModel> results = persons.AsQueryable().ApplyPageFiltering(pagingRequest, false);

        return new PersonQueryResult<PersonUIModel>()
        {
            TotalCount = results.Count,
            Transactions = results.Query.ToList()
        };
    }

    public static QueryablePaging<T> ApplyPageFiltering<T>(this IQueryable<T> query, PagingRequest pagingRequest, bool ignorePaging)
    {
        GridifyMapper<T> gridifyMapper = new GridifyMapper<T>(config => config.IgnoreNotMappedFields = true).GenerateMappings() as GridifyMapper<T>;

        return query.GridifyQueryable(PagingRequestConverter.ToQueryFilter(pagingRequest, ignorePaging), gridifyMapper);
    }

Workaround: Add null coalescing operator in query to default to string.Empty

FirstName = ct.FirstName ?? string.Empty,

Steps to reproduce

• Add row in database which contains null string value
• Add paging request filter to filter on said value (Ex: GridifyQuery.Filter = "FirstName=*ABC)
• Result: Object reference not set to instance of object
• Expected: Value not returned as per filter

[alirezanet]

Hi @riccardorestagno,

Can you please check this discussion, I think you can find another workaround to solve it for now.
This is the default behavior since your filter query gets converted directly to a linq expression, so if you don't add the null check you get the exception.

FYI I'm planning to add a new feature to the next versions for adding the null checks automatically.

[riccardorestagno]

Thanks for the info! My workaround works as well but I'll consider adding null checks in the expressions directly instead of adding a null coalescing operator in all my query properties.