AutoMapper AllowNullCollections Configuration

AutoMapperConfigurator.cs

namespace NullCollectionIssue
{
    using AutoMapper;

    public class ProfileOne : Profile
    {
        public override string ProfileName
        {
            get
            {
                return "ProfileOne";
            }
        }

        protected override void Configure()
        {
            AllowNullCollections = true;
            CreateMap<SourceProfileOne, DestProfileOne>();
        }
    }

    public class ProfileTwo : Profile
    {
        public override string ProfileName
        {
            get
            {
                return "ProfileTwo";
            }
        }

        protected override void Configure()
        {
            CreateMap<SourceProfileTwo, DestProfileTwo>();
        }
    }

    public static class AutoMapperConfigurator
    {
        public static void Configure()
        {
            Mapper.Initialize(x =>
            {
                x.AddProfile<ProfileOne>();
                x.AddProfile<ProfileTwo>();
            });
        }
    }
}

MappingTests.cs

namespace NullCollectionIssue
{
    using AutoMapper;

    using NUnit.Framework;

    [TestFixture]
    public class MappingTests
    {
        [Test]
        public void AutoMapper_Configuration_IsValid()
        {
            AutoMapperConfigurator.Configure();
            Mapper.AssertConfigurationIsValid();
        }

        [Test]
        public void AutoMapper_ProfileOne_AllowsNullCollections()
        {
            AutoMapperConfigurator.Configure();
            Mapper.AssertConfigurationIsValid();

            var source = new SourceProfileOne { Stuff = null };
            var dest = Mapper.Map<SourceProfileOne, DestProfileOne>(source);

            Assert.That(dest, Is.Not.Null);
            Assert.That(dest.Stuff, Is.Null);
        }

        [Test]
        public void AutoMapper_ProfileTwo_DoesntAllowNullCollections()
        {
            AutoMapperConfigurator.Configure();
            Mapper.AssertConfigurationIsValid();

            var source = new SourceProfileTwo { Stuff = null };
            var dest = Mapper.Map<SourceProfileTwo, DestProfileTwo>(source);

            Assert.That(dest, Is.Not.Null);
            Assert.That(dest.Stuff, Is.Not.Null);
            Assert.That(dest.Stuff, Is.Empty);
        }
    }
}

ProfileClasses.cs

namespace NullCollectionIssue
{
    using System.Collections.Generic;

    public class SourceProfileOne
    {
        public ICollection<string> Stuff { get; set; }
    }

    public class DestProfileOne
    {
        public ICollection<string> Stuff { get; set; }
    }

    public class SourceProfileTwo
    {
        public ICollection<string> Stuff { get; set; }
    }

    public class DestProfileTwo
    {
        public ICollection<string> Stuff { get; set; }
    }
}

The tests AutoMapper_Configuration_IsValid and AutoMapper_ProfileTwo_DoesntAllowNullCollections pass, but the test AutoMapper_ProfileOne_AllowsNullCollections fails because dest.Stuff is not null.

From the StackOverflow question - this behaviour was because I was calling the static Mapper.CreateMap in the configure method. Changed it to the instance method, and it worked.

Thanks for sharing. I just set AllowNullCollections = true inside the profile constructor and worked as well.