Interpret query string 'null' as null for specified properties

FromUriNullableAttribute.cs

using System;
using System.Collections.Generic;
using System.Web.Http;
using System.Web.Http.Controllers;
using System.Web.Http.ValueProviders;
using System.Web.Http.ValueProviders.Providers;
using System.Globalization;
using System.Net.Http;
using System.Web.Http.ModelBinding;

public sealed class FromUriNullableAttribute : ModelBinderAttribute
{
    private readonly string[] _nullableColumns;

    public FromUriNullableAttribute(params string[] nullableColumns)
    {
        _nullableColumns = nullableColumns;
    }

    public override IEnumerable<ValueProviderFactory> GetValueProviderFactories(HttpConfiguration configuration)
    {
        return new ValueProviderFactory[] { new NullableValueProviderFactory(_nullableColumns) };
    }
}

public class NullableValueProviderFactory : ValueProviderFactory, IUriValueProviderFactory
{
    private readonly string[] _nullableColumns;

    public NullableValueProviderFactory(string[] nullableColumns)
    {
        _nullableColumns = nullableColumns;
    }

    public override IValueProvider GetValueProvider(HttpActionContext actionContext)
    {
        return new NullableQueryStringValueProvider(actionContext, CultureInfo.InvariantCulture, _nullableColumns);
    }
}

public class NullableQueryStringValueProvider : NameValuePairsValueProvider
{
    private static readonly string[] _nullValues = new string[] { "null", "undefined" };

    private static IEnumerable<KeyValuePair<string, string>> GetQueryNameValuePairs(HttpRequestMessage request, string[] nullableColumns)
    {
        foreach (var pair in request.GetQueryNameValuePairs())
        {
            var isNull = Array.IndexOf(nullableColumns, pair.Key) >= 0 && Array.IndexOf(_nullValues, pair.Value) >= 0;
            yield return isNull ? new KeyValuePair<string, string>(pair.Key, "") : pair;
        };
    }

    public NullableQueryStringValueProvider(HttpActionContext actionContext, CultureInfo culture, string[] nullableColumns) :
        base(GetQueryNameValuePairs(actionContext.ControllerContext.Request, nullableColumns), culture)
    { }
}