Validator忽略RangeAttribute

Question

我有以下实体（这是EF生成的实体的一部分）：

[MetadataType(typeof(ProjectItem_Metadata))]
public partial class ProjectItem : IIdentified, IValidatableObject
{
    internal class ProjectItem_Metadata
    {
        [Editable(false)]
        public int ID { get; set; }

        public int ProjectID { get; set; }

        public int? ReorderParentID { get; set; }

        public int LibraryItemID { get; set; }

        [Range(0, double.MaxValue, ErrorMessageResourceType = typeof(Resources), ErrorMessageResourceName = "QuantityError")]
        public int Quantity { get; set; }

        public float Width { get; set; }

        public float Height { get; set; }

        public float Depth { get; set; }

        public int SheetMaterialID { get; set; }

        public int? BandingMaterialID { get; set; }

        public float MaterialVolume { get; set; }

        public float MaterialWeight { get; set; }

        public double EstimatedItemMass { get; set; }

        public float SurfaceFootage { get; set; }
    }

    public static class Resources
    {
        private static readonly IStringProvider _errors = Strings.Current.GetGroup("ProjectItemErrors");

        // Errors
        public static string QuantityError { get { return _names.GetValueOrDefault("Quantity", "Quantity"); } }
    }

    public IEnumerable<ValidationResult> Validate(ValidationContext a_validationContext)
    {
        IStringProvider _errors = Strings.Current.GetGroup("ProjectItemErrors");

        var libraryItem = LibraryItem;
        if (libraryItem == null)
        {
            using (var context = new YouBuildEntities())
                libraryItem = context.LibraryItems.SingleOrDefault(i => i.ID == LibraryItemID);
        }

        var validationResults = new List<ValidationResult>();

        if (Width < libraryItem.MinWidth)
            validationResults.Add(new ValidationResult(_errors.GetValue("WidthTooSmall", libraryItem.MinWidth), new String[] { "Width" }));

        if (Width > libraryItem.MaxWidth)
            validationResults.Add(new ValidationResult(_errors.GetValue("WidthTooLarge", libraryItem.MaxWidth), new String[] { "Width" }));

        if (Height < libraryItem.MinHeight)
            validationResults.Add(new ValidationResult(_errors.GetValue("HeightTooSmall", libraryItem.MinHeight), new String[] { "Height" }));

        if (Height > libraryItem.MaxHeight)
            validationResults.Add(new ValidationResult(_errors.GetValue("HeightTooLarge", libraryItem.MaxHeight), new String[] { "Height" }));

        if (Depth < libraryItem.MinDepth)
            validationResults.Add(new ValidationResult(_errors.GetValue("DepthTooSmall", libraryItem.MinDepth), new String[] { "Depth" }));

        if (Depth > libraryItem.MaxDepth)
            validationResults.Add(new ValidationResult(_errors.GetValue("DepthTooLarge", libraryItem.MaxDepth), new String[] { "Depth" }));

        return validationResults;
    }
}

当我这样调用Validator.TryValidateObject时：

        var results = new List<ValidationResult>();
        if (!Validator.TryValidateObject(_target, new ValidationContext(_target, null, null), results, true))
        {

        }

验证Height，Width和Depth，但忽略Quantity。我做错了什么？

感谢。