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Null Object Design Pattern






Purpose





Scenario




public class MemberEntity
{ 
   public virtual int Id { get; set; }
   public virtual string FullName { get; set; }
   public virtual string Email { get; set; }
}




MemberEntity memberEntityObject = null;
Console.WriteLine(memberEntityObject.Id);




Picture showing the error message when initializing the class without using the null object design pattern
Click to Enlarge


Null Object Design Pattern Comes Into The Picture




public class MemberEntity
{
        public static readonly MemberEntity NULL = new NullMemberEntity();

        public virtual int Id { get; set; }
        public virtual string FullName { get; set; }
        public virtual string Email { get; set; }
}
class NullMemberEntity : MemberEntity
{
        public override int Id => 0;
        public override string FullName => string.Empty;
        public override string Email => string.Empty;
}




MemberEntity memberEntityObject = MemberEntity.NULL;
Console.WriteLine(memberEntityObject.Id);



Output


Picture showing the output of the null object design pattern
Click to Enlarge


Posted By  -  Karan Gupta
 
Posted On  -  Tuesday, August 30, 2011
 
Updated On  -  Tuesday, July 25, 2023

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