调试易

private int FullLevel { get; set; }
私有属性还有什么意义吗?1.开放FullLevel属性，通过FullLevel的值决定是否跳出循环。
2. Speak(str) 方法返回标识值，比如正常情况返回0， 饿死时返回-1， 然后利用返回值判断：
if(K1.Speak(str)<0)break; 

你想跳出？
这个地方改一下：
while (机器人.FullLevel>=0)
            {
                string str = Console.ReadLine();
                K1.Speak(str);
            }
这个地方改一下，试试
public static int FullLevel;

//简单的修改了一下
 class Program
    {
        static void Main(string[] args)
        {
            机器人 K1 = new 机器人();
            K1.Name = "小K";
            K1.Eat(5);
            K1.SayHello();
            while (机器人.FullLevel>=0)
            {
                string str = Console.ReadLine();
                K1.Speak(str);
            }
            Console.ReadKey();
        }
    }    class 机器人
    {
        public string Name { get; set; }        public static int FullLevel;        public void SayHello()
        {
            Console.WriteLine("你好，我叫：{0},有什么想问的吗？", Name);
            Console.WriteLine("");
        }        public void Eat(int foodCount)
        {
            if (FullLevel > 100)
            {
                return;
            }
            FullLevel = FullLevel + foodCount;
        }        public void Speak(string str)
        {
            if (FullLevel <= 0)
            {
                Console.WriteLine("饿死了，不说了");
            }
            else
            {
                if (str.Contains("姓名") || str.Contains("名字"))
                {
                    this.SayHello();
                }
                else if (str.Contains("女朋友"))
                {
                    Console.WriteLine("年龄小，不考虑！");
                    Console.WriteLine("");
                }
                else
                {
                    Console.WriteLine("听不懂");
                    Console.WriteLine("");
                }
               
            }            FullLevel--;        }
    }

你把代码改成下面的试试看
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
namespace 面向对象版聊天机器人
{
    class Program
    {
        static void Main(string[] args)
        {
            机器人 K1 = new 机器人();
            K1.Name = "小K";
            K1.Eat(5);
            K1.SayHello();
            while (true)
            {
                string str = Console.ReadLine();
               if(K1.Speak(str)<0){
                   break;
                }
            }
            Console.ReadKey();
        }
    }
    class 机器人
    {
        public string Name { get; set; }
 
        private int FullLevel { get; set; }
 
        public void SayHello()
        {
            Console.WriteLine("我叫：{0}", Name);
        }
 
        public void Eat(int foodCount)
        {
            if (FullLevel > 100)
            {
                return;
            }
 
             
            FullLevel = FullLevel + foodCount;
        }
 
        public int Speak(string str)
        {
            if (FullLevel <= 0)
            {
                Console.WriteLine("饿死了，不说了");
                return -1;
            }
                 
 
            if (str.Contains("姓名") || str.Contains("名字"))
            {
                this.SayHello();
            }
            else if (str.Contains("女朋友"))
            {
                Console.WriteLine("年龄小，不考虑！");
            }
            else
            {
                Console.WriteLine("听不懂");
            }
            FullLevel--;
            return FullLevel;
 
        }
    }
}