反射取值问题，求指点

   public class A
    {
        public int Id { get; set; }
        B model = new B();
        public B Model
        {
            get { return model; }
            set { model = value; }
        }
    }

    public class B
    {
        public int Id { get; set; }
    }

    public void Reflection()
    {
        A a = new A();
        PropertyInfo[] Arr = a.GetType().GetProperties();
        Dictionary<string, object> dic = new Dictionary<string, object>();
        foreach (PropertyInfo item in Arr)
        {
            //当获取的属性的类型是一个类时，就会报出“为将对象引用设置到对象的实例”的异常
            dic.Add(item.Name,item.GetValue(a,null));
        }
    }

 dic.Add(item.Name,item.GetValue(a,null));