3 tables, 3 classes, help designing my classes effectively

Question

I have 3 database tables, all of them have the same 5 columns. They differ in that table#2 and table#3 each have another ID column in them.

I don't want to create 3 seperate classes for this, but the problem is in my database helper class I have a method that loads the classes, like:

public static LoadClass1(SqlDataReader reader)
{
     Class1 c1 = new Class1();

     c1.prop1 = (int)reader["prop1"]

}

I don't want to have to create 3 seperate load helper methods, and have to copy the code over on all of them. (I don't mind creating 3, but only having to set the fields that are different in each one).

Answer 1

You could possibly create a base class with all the common fields, then have other classes that extend your base class containing the extra fields.

what i had in mind was

class MyBase
{
   public MyBase()
   {
     // load the base class stuff.
   }
   int f1;
   int f2;
   int f3;
   int f4;
   int f5;
}

class MyClass2 : MyBase
{
   public MyClass2() : base()
   {
     // load the MyClass2 f6
   }

   int f6;
}

class MyClass3 : MyBase
{
   public MyClass3() : base()
   {
     // load the MyClass3 f7
   }

   int f7;
}

Answer 2

Four methods: one that loads the core fields, three others that call the core method and load the extra fields. This would work best with a base class with the core properties, and 3 subclasses.

//Psuedo code, obviously not exact
//Don't hate
public abstract class Core
{
    int field1;
    int field2;
    int field3;
    int field4;
    int field5;
}

public class Sub1 : Core 
{
    field 6;
}

...

public static void LoadCore(Core c, DataTable dt)
{
    c.field1 = dt.getField1(); //Really a database value
    c.field2 = dt.getField2();
    c.field3 = dt.getField3();
    c.field4 = dt.getField4();
    c.field5 = dt.getField5();
}

public static Sub1 LoadSub1()
{
    Sub1 s = new Sub1();
    LoadCore(s, MY_DATA_TABLE);
    s.field6 = MY_DATA_TABLE.getField6();
}

Answer 3

If you don't mind using reflection, something like this could be adapted to suit your needs:

Generic List Provider

You'd just need to return a single T instead of a list of them.

Hope it helps.

Answer 4

You could get the table name via GetSchemaTable with the BaseTableName property and retrieve your field accordingly.