How to avoid duplication?

I am making a C # application. The application has two classes and several methods. While writing the code, I came across a problem. I am using the same two variables (XList and YList) and one method in both classes. And I probably need more classes with this code. So I created a duplication problem. Below is a simple version of my code:

public class A {
  private testEntities db = new testEntities();
  public List<int> XList = new List<int>();
  public List<int> YList = new List<int>();

  public void GetAllInfo()
  {
    // Get the data from a database and add to a list
    XList = db.Table1.ToList();
    YList = db.Table2.ToList();
  }

  public void DoStuff()
  {
    // Do Stuff with XList and 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()
  {
    // Get the data from a database and add to a list (the same as in class A)
    XList = db.Table1.ToList();
    YList = db.Table2.ToList();
  }

  public void DoDifferentStuff()
  {
    // Do ddifferent stuff with XList and YList then in class A
  }
}

      

        
        
        
      

    

My question is, is this the best way to solve this duplication problem?

After some research, I found that I can probably solve this with inheritance or composition. I also read that people choose composition over inheritance. So I decided to write the following code to eliminate 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()
  {
    // Get the data from a database and add to a list
    XList = db.Table1.ToList();
    YList = db.Table2.ToList();
  }

  // Implement other methods
}

public class A 
{
  public void MethodName()
  { 
    DataPreparation dataPreparation = new DataPreparation();
    dataPreparation.GetAllInfo();

    UseDataX(dataPreparation.XList);
    UseDataY(dataPreparation.YList);

    // Implementation UseDataX() and UseDataY()
  }
}

public class B 
{
  public void MethodName()
  { 
    DataPreparation dataPreparation = new DataPreparation();
    dataPreparation.GetAllInfo();

    VisualizeDataX(dataPreparation.XList);
    VisualizeDataY(dataPreparation.YList);

    // Implementation VisualizeDataX() and VisualizeDataY()
  }
}

      

        
        
        
      

    

As you can see, I have created a class that processes data from the database. And that class A and B are using DataPreparation class. But is this the best way to solve the duplication problem? Or should I be using inheritance or something else?