c# - How to avoid duplication? -

i'm making c# application. application has 2 classes , multiple methods. while writing code stumbled on problem. use same 2 variables (xlist , ylist) , 1 method in both classes. , need more classes code. created duplication problem. below simple version of code:

public class {   private testentities db = new testentities();   public list<int> xlist = new list<int>();   public list<int> ylist = new list<int>();    public void getallinfo()   {     // data database , add list     xlist = db.table1.tolist();     ylist = db.table2.tolist();   }    public void dostuff()   {     // stuff xlist , ylist   } }  public class b {   private testentities db = new testentities();   public list<int> xlist = new list<int>();   public list<int> ylist = new list<int>();    public void getallinfo()   {     // data database , add list (the same in class a)     xlist = db.table1.tolist();     ylist = db.table2.tolist();   }    public void dodifferentstuff()   {     // ddifferent stuff xlist , ylist in class   } } 

my question best way solve duplication problem?

after research found can solve inheritance or composition. read people choose composition on inheritance. wrote following code solve duplication:

public class datapreparation {   private testentities db = new testentities();   public list<int> xlist = new list<int>();   public list<int> ylist = new list<int>();    public void getallinfo()   {     // data database , add list     xlist = db.table1.tolist();     ylist = db.table2.tolist();   }    // implement other methods }  public class  {   public void methodname()   {      datapreparation datapreparation = new datapreparation();     datapreparation.getallinfo();      usedatax(datapreparation.xlist);     usedatay(datapreparation.ylist);      // implementation usedatax() , usedatay()   } }  public class b  {   public void methodname()   {      datapreparation datapreparation = new datapreparation();     datapreparation.getallinfo();      visualizedatax(datapreparation.xlist);     visualizedatay(datapreparation.ylist);      // implementation visualizedatax() , visualizedatay()   } } 

as can see made class handles getting data database. , class , b use datapreparation class. best way solve duplication? or should use inheritance or different?

i think should have 1 method called dostuff() rather 1 called dostuff() , called dodifferentstuff().

then can create abc implement common code, , have abstract dostuff() method implemented differently in derived classes:

public abstract class base {     private testentities db = new testentities();      public list<int> xlist = new list<int>();     public list<int> ylist = new list<int>();      public void getallinfo()     {         // data database , add list (the same in class a)         xlist = db.table1.tolist();         ylist = db.table2.tolist();     }      public abstract void dostuff(); }  public class a: base {     public override void dostuff()     {         // stuff xlist , ylist     } }  public class b: base {     public override void dostuff()     {         // ddifferent stuff xlist , ylist in class     } } 

(i think it's bad idea have public fields - i'm guessing/hoping sample code , real code doesn't have those...)

other code (except code creates a or b) use object via base class type.