CODEWITHSUNDEEP
vb.netclassstorage
JEV
JEV

Reputation: 2504

VB.NET How to Store Multiple Objects (of different class types)

My brain is fried at the moment, so here's the scenario.

I have a form that adds a member to my VB.NET application.

When I press submit I add their details: name and number as well as what products they want (internet and phone). Internet and Phone are their own class as is member.

I want to add that they HAVE whichever they have chosen and with the member store it.

EDIT:

So it looks like this :

MEMBER : Name- Bob Number- 118 Phone=True Internet = False

That would be one record.

What can I store all 3 in so there is a reference to all 3 of them? It'driving me insane.

I originally had an array which just had true or false for whether they were there, but that was before I implemented classes.

I was also using a collection to store the members, which would contain everything pretty much.

Any ideas?

As what happens is once the member is created (stored) I will go to input how much they have used, and then store that. But to do so I will need access to the internet and phone classes, which are associated with said member.

Upvotes: 0

Views: 2132

Answers (2)

competent_tech
competent_tech

Reputation: 44931

There are two parts to this problem:

  1. How do you store the information in the database?
  2. How do you store the information in the application?

The typical scenario for storage in the database is that Member is the parent record and Internet and Phone are child records, either stored in the same table or in different tables.

My usual preference is to store contact information in a single table with a Type field that delineates the type of data stored in the record and a single field that holds the content associated with the record (i.e. web address, email address, etc.).

In this design, you would have a foreign key reference to the Member primary key in the Contacts table and the Member primary key should not be anything related to the content of the Member record.

For example:

CREATE TABLE Members
(
        /* This table contains current information on a given Member */

        /* The unique id for this record */
      RecordId                   INTEGER          NOT NULL IDENTITY(1,1) ,

        /* The Member's first name */
      FirstName                  NVARCHAR(50)     NOT NULL ,
        /* The Member's middle name */
      MiddleName                 NVARCHAR(50)     NULL ,
        /* the Member's last name */
      LastName                   NVARCHAR(50)     NOT NULL ,

      CONSTRAINT PK_Members PRIMARY KEY
      (
            RecordId
      )
)

CREATE TABLE Contacts
(
        /* The unique id for this record */
      RecordId                   INTEGER          NOT NULL IDENTITY(1,1) ,

        /* The member that this contact is associated with */
      MemberId                  INTEGER          NOT NULL ,
        /* The type of contact. Current values are:
           1  - Internent
           2  - Phone
        */
      Type                       INTEGER          NOT NULL ,
        /* The contact details */
      Reference                   NVARCHAR(MAX)   NOT NULL ,

      CONSTRAINT PK_Contacts PRIMARY KEY
      (
            RecordId
      ) ,

        /* Referential integrity notes:

           If the member is deleted, all associated records in this table will be automatically deleted
        */
      CONSTRAINT FK_Members_C FOREIGN KEY (
            MemberId 
      ) REFERENCES Members (
            RecordId
      ) ON DELETE CASCADE
)

For storing the information in the application I personally prefer mirroring the tables in the database with classes in the application since that is easier to maintain and more extensible:

Public Class Member
    Public Property RecordId As Integer
    Public Property FirstName As String
    Public Property MiddleName As String
    Public Property LastName As String

    Public Property Contacts As New System.Collections.Generic.Dictionary(Of Integer, Contact)

End Class

Public Class Contact
    Public Property RecordId As Integer
    Public Property MemberId As Integer

    Public Enum Types
        None
        Internet
        Phone
    End Enum

    Public Property Type As Types
    Public Property Reference As String
End Class

But you could also manufacture instances of existing classes based on the type as the data is being read from the database and store them in the member.

Upvotes: 0

AndreiM
AndreiM

Reputation: 4598

One solution is to define an interface that defines common properties of your classes. For example, define a Selectable with a getType() method. This interface is implemented by both Phone and Internet. You could then maintain a collection of Selectable objects per user and build your rows by iterating over each user's collection and determining which types of Selectables are present.

Upvotes: 1

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