编辑属性时出现的问题？

Question

    public  class PhotoAlbum : Collection<Photograph>,IDisposable
    {
        private bool _hasChanged = false;        public  bool HasChanged
        {
            get
            {
                if (_hasChanged)                    return true;                foreach (Photograph p in this)
                {
                    if (p.HasChanged)
                        return true;
                    return false;
                }
            }
            internal set
            {
                _hasChanged = value;
                if (value == false)
                {
                    foreach (Photograph p in this)
                        p.HasChanged = false;
                }
            }
        }
        public Photograph Add(string fileName)
        {
            Photograph p = new Photograph(fileName);
            base.Add(p);
            return p;
        }        protected override void InsertItem(int index, Photograph item)
        {
            base.InsertItem(index, item);
            HasChanged = true;
        }
        protected override void RemoveItem(int index)
        {
            Items[index].Dispose();
            base.RemoveItem(index);
            HasChanged = true;
        }
        protected override void SetItem(int index, Photograph item)
        {
            base.SetItem(index, item);
            HasChanged = true;
        }
        public void Dispose()
        {
            foreach (Photograph p in this)
                p.Dispose();
        }
        protected override void ClearItems()
        {
            if (Count > 0)
            {
                Dispose();
                base.ClearItems();
                HasChanged = true;
            }
        }    }
}
编译时报错：错误 1 “Manning.MyPhotoAlbum.PhotoAlbum.HasChanged.get”: 并非所有的代码路径都返回值 C:\Documents and Settings\XuShuXiang\My Documents\Visual Studio 2005\Projects\MyPhotos\MyPhotoAlbum\PhotoAlbum.cs 16 13 MyPhotoAlbum
为什么啊？？？

Answer 1

        public  bool HasChanged 
        { 
            get 
            { 
                if (_hasChanged)                     return true;                 foreach (Photograph p in this)                 { 
                    if (p.HasChanged) 
                        return true; 
                    return false; 
                } 
            } 
            internal set 
            { 
                _hasChanged = value; 
                if (value == false) 
                { 
                    foreach (Photograph p in this) 
                        p.HasChanged = false; 
                } 
            } 你能说一下红字的部分是什么意图么？

Answer 2

        public  bool HasChanged 
        { 
            get 
            { 
                if (_hasChanged)                     return true;                 foreach (Photograph p in this)
                { 
                    if (p.HasChanged) 
                        return true; 
                    return false; 
                } 
            } 
            internal set 
            { 
                _hasChanged = value; 
                if (value == false) 
                { 
                    foreach (Photograph p in this) 
                        p.HasChanged = false; 
                } 
            } 

Answer 3

internal set 没有返回值！

Answer 4

说真的，不太明白你那儿的意图，不知道你是不是要检查所有的Photograph，只要有被修改的就返回true？
如果是，get方法：            get  
            {  
                if (_hasChanged)                      return true;  
                bool result=false;
                foreach (Photograph p in this) 
                {  
                    if (p.HasChanged)  
                    {  
                       result=true;
                       break;
                    }  
                }  
               return result;
            }  

Answer 5

恩，是要遍历Photograph是否被修改的。谢谢dancigbit！真心感谢您的帮助