What is the use of Is Required Property in Data Contracts?

Data Contracts, is used to define Required or NonRequired data members. It can be done with a property named IsRequired on DataMember attribute.


[DataContract]
public class test
{
      [DataMember(IsRequired=true)]
      public string NameIsMust;

      [DataMember(IsRequired=false)]
      public string Phone;          
}