Properties private set

Question

I know it only allows the class to set it  but what is the point   How do I solve the problem of having readonly ids   Say I have a person class   public class Person               public string Name   get   set            public int Id   get  private set            public int Age   get  set            And this is in an Entities dll  used by a GUI  BL and DAL   The GUI calls the BL      List lt Person gt  p    BL PeopleBL GetPeople      For the sake of the example calls the DAL       while dr read          returnPersonList add  new Person  Age dr GetInt32 1   Id dr GetInt32 0   Name dr GetString 2            of course I cannot do that cause Id is a private set  What is the proper way to do this   How can I let the BL Dal set the Id  but not on the GUI   Or is this not even the proper use of a private set     I just wanted to add that this is your typical DB app  where the pk is the Id and should not be changed  only by the BL DAL

User · Answer

You can let the user set a read-only property by providing it through the constructor   public class Person       public Person int id                this Id   id             public string Name   get   set        public int Id   get  private set        public int Age   get  set

User · Answer

while dr read          returnPersonList add           new Person dr GetInt32 1   dr GetInt32 0   dr GetString 2         where   public class Person       public Person int age  int id  string name                 Age   age          Id   id          Name   name

User · Answer

This is normally the case then the ID is not a natural part of the entity  but a database artifact that needs be abstracted away   It is a design decision - to only allow setting the ID during construction or through method invocation  so it is managed internally by the class   You can write a setter yourself  assuming you have a backing field   private int Id   0  public void SetId  int id      this Id   id      Or through a constructor   private int Id   0  public Person  int id      this Id   id

User · Answer

The two common approaches are either that the class should have a constructor for the DAL to use  or the DAL should use reflection to hydrate objects

User · Answer

Perhaps  you can have them marked as internal  and in this case only classes in your DAL or BL  assuming they are separate dlls  would be able to set it    You could also supply a constructor that takes the fields and then only exposes them as properties

User · Answer

This is one possible solution although not very clean    Make the property you need to expose to BAL  amp  DAL internal Mark BAL dll  amp  DAL dll Internal Visible in assemblyinfo cs     public class Person       public Person int id                 this Id id             public string Name   get   set        public int Id   get  internal set        public int Age   get  set        AssemblyInfo cs for Entities dll   assembly  InternalsVisibleTo  DAL    InternalsVisibleTo  BAL      That way all your internals will be visible to DAL  amp  BAL  This may not be desirable but I m just suggesting one possible solution

User · Answer

Depending on the scope of my application  I like to put the object hydration mechanisms in the object itself   I ll wrap the data reader with a custom object and pass it a delegate that gets executed once the query returns   The delegate gets passed the DataReader   Then  since I m in my smart business object  I can hydrate away with my private setters   Edit for Pseudo-Code  The  DataAccessWrapper  wraps all of the connection and object lifecycle management for me   So  when I call  ExecuteDataReader   it creates the connection  with the passed proc  there s an overload for params   executes it  executes the delegate and then cleans up after itself   public class User       public static List lt User gt  GetAllUsers                 DataAccessWrapper daw   new DataAccessWrapper            return  List lt User gt   daw ExecuteDataReader  MyProc   new ReaderDelegate ReadList                protected static object ReadList SQLDataReader dr                List lt User gt  retVal   new List lt User gt             while dr Read                          User temp   new User                temp Prop1   dr GetString  Prop1                temp Prop2   dr GetInt  Prop2                retVal Add temp                     return retVal

User · Answer

Or you can do  public class Person       public Person int id                 this Id id             public string Name   get   set        public int Id   get  private set        public int Age   get  set

User · Answer

Maybe I m misunderstanding  but if you want truly readonly Ids why not use an actual readonly field   public class Person      public Person int id             m id   id           readonly int m id     public int Id   get   return m id

[c#] Properties private set;

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