我最终避免了MemberList.None，并创建了一个扩展方法IgnoreAllNonExisting（）作为ForAllOtherMembers（）的替代方法。注意，这并不理想，因为它依赖于AutoMapper内部，但满足了我的需要。

public static class AutoMapperExtensions
{
    public static IMappingExpression<TSource, TDestination> IgnoreAllNonExisting<TSource, TDestination>
    (this IMappingExpression<TSource, TDestination> expression)
    {
        // This is not an ideal way to depend on internals of AutoMapper to find existing mapping to ignore the rest.
        //  Given the breaking change of AutoMapper since 11.0 and the amount of dependency we have on IgnoreAllNonExisting method
        // I chose to go with this approach. Longer term we may need to move to explicit mapping
        // using a type converter for each of IgnoreAllNonExisting() dependency
        var propInfo = expression
                        .GetType()
                        .GetProperty(
                            "MemberConfigurations",
                            BindingFlags.Instance | BindingFlags.NonPublic);

        var explicitMappings = (List<IPropertyMapConfiguration>)propInfo.GetValue(expression, null);

        var flags = BindingFlags.Public | BindingFlags.Instance;
        var destinationProperties = typeof(TDestination).GetProperties(flags);

        foreach (var property in destinationProperties)
        {
            if (explicitMappings != null && explicitMappings.Any(r => string.Compare(r.DestinationMember.Name, property.Name) == 0))
                continue;

            expression.ForMember(property.Name, opt => opt.Ignore());
        }

        return expression;
    }
}