Implementing Entity Validation - ASP.NET Dynamic Data - page 244

EnumDataTypeAttribute
Consider the OrderStatus enumerated type (or enum for short) defined in the sample
project for the Order entity:
public enum OrderStatus: byte
{
Draft = 0,
Submitted = 1,
Paid = 2,
Fulfilled = 3
}
Due to the limitations in the current version of the Entity Framework, the OrderStatus
property of the Order entity class is actually of type Byte and allows values other than the
0, 1, 2, and 3 defined in the enum. Even without the limitation, you could cast any value
of a compatible numeric type, such as 10 of type Byte in this case, to the enum type,
OrderStatus, and store it a variable or property of the enum type.
NOTE
The .NET Framework specifically allows variables of an enum type to store values that
are not defined in the enum. This allows class library developers to add new items to
existing enum types without breaking binary compatibility with applications that were
compiled with the original version of a class library.
The EnumDataTypeAttribute verifies that a value is actually defined in the specified
enumerated type. You can apply it to the OrderStatus property of the Order class to
ensure that only values defined in the OrderStatus enum can be stored in it:
[ EnumDataType(typeof(OrderStatus)) ]
public object OrderStatus { get; set; }
You can verify that this attribute works by writing the following test. It sets the
OrderStatus property with the value 10, which is not defined in the OrderStatus enum. As
expected, the validation code in the SaveChanges method detects this error and throws
the ValidationException :
[TestMethod]
[ExpectedValidationException(MemberName = “OrderStatus” )]
public void OrderStatus_RejectsInvalidValues()
{
using (new TransactionScope())
using (var context = new NorthwindEntities())
{
var order = CreateOrder();
order.OrderStatus = 10;
context.Orders.AddObject(order);