propertyinjectionD.cs

public class School
{
    private ISchool _school;

    public ISchool school
    {
        get
        {
            if (_school == null) school = new HavardUniversity();
            return _school;
        }
        set { _school = value; }
    }

    public string AttendClass(string student)
    {
        return school.Learn(student);
    }
}