EF4 MVC3 model state validation - asp.net-mvc-3

Question

Using this model:
public class Cases
{
//case data model for call center
//implement lists for all related child tables too
[Key]
public int CasesID { get; set; }
public string CaseNumber { get; set; }
[Required(ErrorMessage = "Customer is Required")]
public int CustomerID { get; set; }
public virtual Customer Customer { get; set; }
[MaxLength(50)]
public string UserName { get; set; } //get user name from the aspnet membership
[Required(ErrorMessage = "Case Category is Required")]
public int CaseCategoryID { get; set; }
[Required(ErrorMessage = "Technician is Required")]
public int TechnicianID { get; set; }
public virtual Technician Technicians { get; set; }
[Required(ErrorMessage = "Engine Model is Required")]
public int EngineModelID { get; set; }
public virtual EngineModel EngineModel { get; set; }
[MaxLength(50)]
public string BMSWorkorder { get; set; }
[MaxLength(50)]
[Required(ErrorMessage = "Status is Required")]
public string CaseStatus { get; set; }
[MaxLength(50)]
public string OpenedBy { get; set; }
[Required(ErrorMessage = "Opened Date is Required")]
[DataType(DataType.DateTime)]
public DateTime? OpenedDate { get; set; }
[MaxLength(50)]
public string ClosedBy { get; set; }
[DataType(DataType.DateTime)]
public DateTime? ClosedDate { get; set; }
[MaxLength(50)]
[Required(ErrorMessage="Caller First Name is Required")]
public string CallerFirstName { get; set; }
[MaxLength(50)]
[Required(ErrorMessage = "Caller Last Name is Required")]
public string CallerLastName { get; set; }
[MaxLength(100)]
public string AdditionalContact { get; set; }
[MaxLength(10)]
[Required(ErrorMessage = "Qualified is Required")]
public string Qualified { get; set; }
public string Description { get; set; }
[MaxLength(50)]
[Required(ErrorMessage = "ESN is Required")]
public string ESN { get; set; }
[MaxLength(50)]
[Required(ErrorMessage = "Mileage is Required")]
public string Mileage { get; set; }
[DataType(DataType.Date)]
public DateTime? DateInService { get; set; }
[MaxLength(50)]
public string ESTR { get; set; }
[MaxLength(50)]
[Required(ErrorMessage = "EDS is Required")]
public string EDS { get; set; }
[MaxLength(50)]
public string GensetSerialNumber { get; set; }
[MaxLength(50)]
public string GensetModelNumber { get; set; }
//child Case Notes records
public virtual ICollection<CaseNotes> CaseNotes { get; set; }
//child case attachment records
public virtual ICollection<Attachment> Attachments { get; set; }
//child case complaint records
public virtual ICollection<CaseComplaint> CaseComplaint { get; set; }
//tracking fields
public DateTime? CreatedOn { get; set; }
[MaxLength(50)]
public string CreatedBy { get; set; }
public DateTime? ModifiedOn { get; set; }
[MaxLength(50)]
public string ModifiedBy { get; set; }
}
I am wondering why even though only some of the properties are marked required, the modelstate does not get set valid unless all properties have values when saving.
Am I doing something wrong?
EDIT
Here are my razor elements for the dropdownlist fields in question:
#Html.DropDownList("Qualified", String.Empty)
#Html.ValidationMessageFor(model => model.Qualified)
#Html.DropDownList("EngineModelID", String.Empty)
#Html.ValidationMessageFor(model => model.EngineModelID)
#Html.DropDownList("CaseCategoryID", String.Empty)
#Html.ValidationMessageFor(model => model.CaseCategoryID)

Answer 1

The EngineModelID and CaseCategoryID properties must be nullable integers on your view model if you want to allow empty values. Oooops, you are not using view models.
ASP.NET MVC automatically makes non-nullable types required. You could disable this explicitly in your Application_Start:
DataAnnotationsModelValidatorProvider.AddImplicitRequiredAttributeForValueTypes = false;
But if you want to do the things properly you should use view models.
The following is absolutely horrible:
#Html.DropDownList("CaseCategoryID", String.Empty)
I guess you have stuffed a SelectList in a ViewBag.CaseCategoryID so the CaseCategoryID does 2 things at the same time: it represents a list and a selected scalar value.
With view models you would use the strongly typed version of those helpers:
#Html.DropDownListFor(x => x.CaseCategoryID, Model.CaseCategories)
where CaseCategories will be an IEnumerable<SelectListItem> property on your view model that the controller would populate.