gistfile1.cs

	public class Foo
	{
		public Foo()
		{
			items = new HashedSet<FooItem>();
			//Items = new HashedSet<FooItem>();
		}
		private readonly ICollection<FooItem> items;

		//this fail
		public virtual ICollection<FooItem> Items
		{
			get { return items; }
		}
		//this works
		//public virtual ICollection<FooItem> Items { get; private set; }

		public string Test { get; set; }
	}

	public class FooItem
	{
		public string Test { get; set; }
	}

	public class Bar
	{
		public Bar() { Items = new List<BarItem>(); }
		public ICollection<BarItem> Items { get; private set;}
		public string Test { get; set; }
	}

	public class BarItem
	{
		public string Test { get; set; }
	}

	
	
	[TestFixture]
	public class TestMapper
	{
		[Test]
		public void Test()
		{
			AutoMapper.Mapper.CreateMap<Bar, Foo>()
				.ForMember(m => m.Items, m => m.UseDestinationValue());

			AutoMapper.Mapper.CreateMap<BarItem, FooItem>();

			var bar = new Bar();
			bar.Items.Add(new BarItem{Test = "Baz"});

			var foo = AutoMapper.Mapper.Map<Bar, Foo>(bar);
			foo.Items.Count.Should().Be.EqualTo(1);
		}
	}