[Q] Range doesn't include null fields in database

[enisn]

Problem

By default, Range<T> doesn't include null values, it generates only GTE (>=) and LTE (<=) comparison. So null values don't match these arithmetic comparison because they're not greater or lesser, they're just NULL.

[enisn]

By the way, I got some feedbacks about including nulls in range query. There is a way to include nulls in your query:

• Overriding Range!

Following class will solve this problem. But it's not a best practise so it'll not be inlcuded in AutoFilterer library by default. You can create in your project and use if you really need.

using System;
using System.Linq.Expressions;
using System.Reflection;
using AutoFilterer.Types;

namespace AutoFilterer.Types
{
        public class RangeOrNull<T> : Range<T> where T : struct, IComparable
        {
            public override Expression BuildExpression(Expression body, PropertyInfo targetProperty, PropertyInfo filterProperty, object value)
            {
                var rangeComparison = base.BuildExpression(body, targetProperty, filterProperty, value);
                
                var nullComparison = Expression.Equal(Expression.Property(body, targetProperty.Name), Expression.Constant(null));

                return  Expression.Or(rangeComparison, nullComparison);
            }
        }
}

• Then use RangeOrNull instead of Range

- public Range<DateTime> PublishDate { get; set; }
+ public RangeOrNull<DateTime> PublishDate { get; set; }