Port of http://martinburrows.net/blog/2016/01/18/automatic-unflattening-with-automapper/ that works with AutoMapper 3.x and C# 5

MappingExtensions.cs

public static class MappingExtensions
{
    public static void Unflatten<T>(this IMemberConfigurationExpression<T> config)
    {
        config.ResolveUsing(resolutionResult =>
        {
            var context = resolutionResult.Context;
            var prefix = context.MemberName;
            var destProperties = context.DestinationType.GetProperties();
            var dest = Activator.CreateInstance(context.DestinationType);

            foreach (var sourceMember in context.SourceType.GetProperties())
            {
                var matchedProperty = destProperties.FirstOrDefault(p => sourceMember.Name == prefix + p.Name);
                if (matchedProperty != null) matchedProperty.SetValue(dest, sourceMember.GetValue(context.SourceValue));
            }

            return dest;
        });
    }
}