Q:

DataContract attribute -WCF

Is DataContract attribute is deprecated in ASP.NET 4.0 WCF ? I can see only DataContractFormat attribute.
I can't apply DataContractFormat attribute over struct.
example
[DataContractFormat]
public struct Contact
{
  public string firstName;
  public string lastName;
}

It throws an error saying that DataContractFormat artribute can only be used on class, interface and methods.

A:

No, the .NET 4 still contains the DataContractAttribute:
http://msdn.microsoft.com/en-us/library/system.runtime.serialization.datacontractattribute%28v=VS.100%29.aspx
and it should be able to be applied to class or struct.

A:

You have to add a reference to the System.Runtime.Serialization assembly (right click References, add ref...)

A:

DataContract is not deprecated - where the heck did you get that idea from?
DataCOntractFORMAT is something totally different. I suggest you please read the documentation ;) Helps a lot. Will also explain what DataContractFormat is for.
http://msdn.microsoft.com/en-us/library/system.servicemodel.datacontractformatattribute.aspx
As you can see in the example this attribute goes on the class/interface that defines the SERVICE CONTRACT. It controls how for that service data serializaton is (guess what) formatted.

