dogList对于方法Main是本地的.相反，您要做的是将dogList放置在该范围之外.

dogList is local to the method Main. What you want to do instead is to place dogList outside of that scope.

public class Program
{
    static List<Dog> dogList = new List<Dog>();

...

或者，您也可以将列表发送到添加方法中.

Alternately you can send the list into your add method.