How to avoid instantiating an object every single time so I can add objects to a list of objects contained within that first object?

Question

Each time I click on a button I would like to add a new location via the AddLocation method to a list of LocationSpecs objects. But with the code as is, a new officeRental object is created every time I click on the btnAddLocation button with a new list of LocationSpecs objects. So every time I click on the button the previous object is lost from memory. How can I modify this code so in the end I can have only one list of LocationSpecs objects inside a single officeRental object?

   private void btnAddLocation_Click(object sender, EventArgs e)
   {
       string name = txtName.Text;
       string neighborhood = txtNeighborhood.Text;
       LocationSpecs location = new LocationSpecs(name, neighborhood);
       OfficeRental officeRental = new OfficeRental();
       officeRental.AddLocation(location);
       MessageBox.Show(name + " in " + neighborhood + " added.");
   }

  public class OfficeRental : IOfficeRental
  {
   public List<LocationSpecs> LocationSpecs { get; set; }
   public OfficeRental()
   {
       LocationSpecs = new List<LocationSpecs>();

   }
   public void AddLocation(LocationSpecs locationSpecs)
   {
       // throw new NotImplementedException();
       LocationSpecs.Add(locationSpecs);
   }

 public class LocationSpecs
 {
   public string Name { get; }
   public string Neighborhood { get; }

   public LocationSpecs(string name, string neighborhood)
   {
       if (string.IsNullOrWhiteSpace(name)) throw new ArgumentException(nameof(name));
       if (string.IsNullOrWhiteSpace(neighborhood)) throw new >ArgumentException(nameof(neighborhood));

       Name = name;
       Neighborhood = neighborhood;
   }

}

Answer 1

You should move the line:

OfficeRental officeRental = new OfficeRental();

from the button click function and make it a Class member variable, similar to:

class <yourFormName>
{
    OfficeRental officeRental = new OfficeRental();
    ... // the rest of your code
}

This will mean that the officeRental object is now visible throughout the whole class (a class member variable) instead of just being used in the single button click handler.