新手求解解决方案

新手求解
namespace 类的应用_猫_
{
  class Class1
  {
  public int weight;
  public string color;
  public int age;
  public void Input()
  {
  Console.Write("请输入猫的体重：");
  this.weight = Convert.ToInt32(Console.ReadLine());
  Console.WriteLine();
  Console.Write("请输入猫的颜色：");
  this.color = Console.ReadLine();
  Console.WriteLine();
  Console.Write("请输入猫的年龄：");
  this.age = Convert.ToInt32(Console.ReadLine());

  }
  public void Output()
  {
  Console.WriteLine("猫的体重为:",this.weight);
  Console.WriteLine("猫的颜色为：",this.color);
  Console.WriteLine("猫的年龄为:",this.age);
  }
  public void Modify()
  {
  Console.WriteLine("信息修改中...");
  Console.Write("体重");
  this.weight = Convert.ToInt32(Console.ReadLine());
  Console.Write("颜色：");
  this.color = Console.ReadLine();
  Console.Write("年龄:");
  this.age =Convert.ToInt32(Console.ReadLine());
  }
  }
}
namespace 类的应用_猫_
{
  class Program
  {
  static void Main(string[] args)
  {
  Class1 a = new Class1();
  a.Input();
  a.Output();
  a.Modify();
  Console.ReadLine();
  }
  }
}
为什么不能运行呢？

[解决办法]

C# code

        public void Output()        {            Console.WriteLine("猫的体重为: {0}", weight);            Console.WriteLine("猫的颜色为：{0}", color);            Console.WriteLine("猫的年龄为:{0}", age);        }
[解决办法]
,  改为  +
Console.WriteLine("猫的体重为: "+this.weight);
[解决办法]
C# code
        Console.WriteLine("猫的体重为: " + weight);            Console.WriteLine("猫的颜色为：" + color);            Console.WriteLine("猫的年龄为:" + age);