Programming WCF Services

Enumerations

Enumerations are always serializable by definition. When you define a new enum, there is no need to apply the DataContract attribute on it, and you can freely use it in a data contract, as shown in Example 3-9. All the values in the enum will implicitly be included in the data contract.

Example 3-9. Using an enum in a data contract

enum ContactType
{
   Customer,
   Vendor,
   Partner
}

[DataContract]
struct Contact
{
   [DataMember]
   public ContactType ContactType;

   [DataMember]
   public string FirstName;

   [DataMember]
   public string LastName;
}

If you want to exclude certain enum values from the data contract, you need to first decorate the enum with the DataContract attribute. Then, explicitly apply the EnumMemberAttribute to all enum values you want to include in the enum data contract. The EnumMember attribute is defined as:

[AttributeUsage(AttributeTargets.Field,Inherited = false)]
public sealed class EnumMemberAttribute : Attribute
{
   public string Value
   {get;set;}
}

Any enum value not decorated with the EnumMember attribute will not be part of the data contract for that enum. For example, this enum:

[DataContract]
enum ContactType
{
   [EnumMember]
   Customer,

   [EnumMember]
   Vendor,

   //Will not be part of data contract
   Partner
}

will result in this wire representation:

enum ContactType
{
   Customer,
   Vendor
}

The other use for the EnumMember attribute is to alias certain enum values to an already existing enum data contract using the Value property. For example, this enum:

[DataContract] enum ...