c# - 使用 winforms 实现观察者模式

Question

我有一个对象集合，我的许多表单(使用 WeifenLuo.WinFormsUI.Docking)需要与之交互。

即如果集合以一种形式进行了添加(或删除)，则其他形式通过刷新它们的 View 来响应。

显然，观察者模式在这里是一个不错的选择。但是，我在尝试在我的程序中实现它时遇到了问题。

首先，似乎最好为我的集合创建一个观察者类，如下所示:

public class DataCollectionObserver : Form
{
    internal static void DataCollectionRegister(DataCollection dataCollection)
    {
        dataCollection.ImageAdded += new EventHandler(dataAdded);
        dataCollection.ImageRemoved += new EventHandler(dataRemoved);
        dataCollection.ImageIndexChanged += new EventHandler(dataIndexChanged);
        dataCollection.ImageListCleared += new EventHandler(dataListCleared);
    }

    internal static void DataCollectionUnRegister(DataCollection dataCollection)
    {
        dataCollection.ImageAdded -= new EventHandler(dataAdded);
        dataCollection.ImageRemoved -= new EventHandler(dataRemoved);
        dataCollection.ImageIndexChanged -= new EventHandler(dataIndexChanged);
        dataCollection.ImageListCleared -= new EventHandler(dataListCleared);
    }

    internal static void dataAdded(object sender, EventArgs e) {}
    internal static void dataRemoved(object sender, EventArgs e) {}
    internal static void dataIndexChanged(object sender, EventArgs e) {}
    internal static void dataListCleared(object sender, EventArgs e) {}
}

然后覆盖子类表单中的基本事件处理程序？

但是，我不能这样做并使用 WeifenLuo.WinFormsUI.Docking 库...

好吧，我可以让 DataCollectionObserver 从 WeifenLuo.WinFormsUI.Docking 继承 DockContent，但这会造成我需要两个 DataCollectionObserver 类的情况 -一个继承 Form 另一个继承 DockContent :-[或者，我可以使 DataCollectionObserver 成为一个接口(interface)，但这仍然给我留下了重复的代码……

那么，有人在这里有什么建议吗？我是否遗漏了一些明显的东西，或者这是为了简单起见“必须完成”代码重复的情况？

---

编辑://

我在收到表单通知时没有遇到任何问题。事实上，整个事情现在正在运作。我问的原因是，由于 block 复制和粘贴代码以我拥有的这四种不同形式订阅收集事件并取消订阅 Form.Closing()，所以整个事情“闻起来”。

我想做的是在一个地方实现我复制并粘贴到这四个表单的行为，并让应该接收集合更改通知的表单根据需要实现该行为。

希望这能让事情变得更清楚？

FWIW，这是我的收藏类:

using System;
using System.Collections;
using System.Reflection;

namespace MyNameSpace.Collections
{
    /// <summary>
    /// Generic Collection of Objects with Events
    /// </summary>
    public class CollectionWithEvents<T> : CollectionBase
    {
        public bool SuppressEventNotification
        {
            get;
            set;
        }

        public CollectionWithEvents()
        {
            SuppressEventNotification = false;
        }

        #region Events
        /// <summary>
        /// Raises before an item is added to the list.
        /// </summary>
        public event EventHandler<ItemEventArgs<T>> BeforeItemAdded;

        /// <summary>
        /// Raises when an item is added to the list.
        /// </summary>
        public event EventHandler<ItemEventArgs<T>> ItemAdded;

        /// <summary>
        /// Raises before a collection of items is added to the list.
        /// </summary>
        public event EventHandler<ItemsEventArgs<T>> BeforeItemsAdded;

        /// <summary>
        /// Raises when a collection of items is added to the list.
        /// </summary>
        public event EventHandler<ItemsEventArgs<T>> ItemsAdded;

        /// <summary>
        /// Raises before an item is changed in the list.
        /// </summary>
        public event EventHandler<ItemEventArgs<T>> BeforeItemChanged;

        /// <summary>
        /// Raises when an item is changed in the list.
        /// </summary>
        public event EventHandler<ItemEventArgs<T>> ItemChanged;

        /// <summary>
        /// Raises before an item is removed from the list.
        /// </summary>
        public event EventHandler<ItemEventArgs<T>> BeforeItemRemoved;

        /// <summary>
        /// Raises when an item is removed from the list.
        /// </summary>
        public event EventHandler<ItemEventArgs<T>> ItemRemoved;

        /// <summary>
        /// Raises when the items are cleared from the list.
        /// </summary>
        public event EventHandler<EventArgs> ItemsCleared;
        #endregion

        public T this[int index]
        {
            get { return (T)this.List[index]; }
            set
            {
                if (!SuppressEventNotification)
                {
                    OnBeforeItemChanged(this, new ItemEventArgs<T>(value));
                }

                this.List[index] = value;

                if (!SuppressEventNotification)
                {
                    OnItemChanged(this, new ItemEventArgs<T>(value));
                }
            }
        }

        public int Add(T item)
        {
            if (!SuppressEventNotification)
            {
                OnBeforeItemAdded(this, new ItemEventArgs<T>(item));
            }

            int retValue = this.List.Add(item);

            if (!SuppressEventNotification)
            {
                OnItemAdded(this, new ItemEventArgs<T>(item));
            }

            return retValue;
        }

        public void AddRange(Collection<T> collection)
        {
            T[] tmp = new T[collection.Count];

            collection.CopyTo(tmp, 0);

            AddRange(tmp);
        }

        public void AddRange(T[] collection)
        {
            if (!SuppressEventNotification)
            {
                OnBeforeItemsAdded(this, new ItemsEventArgs<T>(collection));
            }

            this.AddRange(collection);

            if (!SuppressEventNotification)
            {
                OnItemsAdded(this, new ItemsEventArgs<T>(collection));
            }
        }

        public bool Contains(T item)
        {
            return this.List.Contains(item);
        }

        public void CopyTo(Array array, int index)
        {
            this.List.CopyTo(array, index);
        }

        public int IndexOf(T item)
        {
            return this.List.IndexOf(item);
        }

        public void Insert(int index, T item)
        {
            this.List.Insert(index, item);
        }

        public void Remove(T item)
        {
            if (!SuppressEventNotification)
            {
                OnBeforeItemRemoved(this, new ItemEventArgs<T>(item));
            }

            T tmp = (T)item;

            this.List.Remove(item);

            if (!SuppressEventNotification)
            {
                OnItemRemoved(this, new ItemEventArgs<T>(tmp));
            }

            tmp = default(T);
        }

        public void Sort(string Property, Common.SortOrder Order)
        {
            Common.GenericComparer genericComparer = new Common.GenericComparer(Property, Order);
            this.InnerList.Sort(genericComparer);
        }

        #region Event Methods
        /// <summary>
        /// Raised before an Item is added to the list.
        /// </summary>
        /// <param name="sender">object</param>
        /// <param name="e">ItemEventArgs</param>
        protected virtual void OnBeforeItemAdded(object sender, ItemEventArgs<T> e)
        {
            if (BeforeItemAdded != null)
            {
                BeforeItemAdded(sender, e);
            }
        }

        /// <summary>
        /// Raised when an Item is added to the list.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e">ItemEventArgs</param>
        protected virtual void OnItemAdded(object sender, ItemEventArgs<T> e)
        {
            if (ItemAdded != null)
            {
                ItemAdded(sender, e);
            }
        }

        /// <summary>
        /// Raised before a collection of Items is added to the list.
        /// </summary>
        /// <param name="sender">object</param>
        /// <param name="e">ItemEventArgs</param>
        protected virtual void OnBeforeItemsAdded(object sender, ItemsEventArgs<T> e)
        {
            if (BeforeItemsAdded != null)
            {
                BeforeItemsAdded(sender, e);
            }
        }

        /// <summary>
        /// Raised when a collection of Items is added to the list.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e">ItemEventArgs</param>
        protected virtual void OnItemsAdded(object sender, ItemsEventArgs<T> e)
        {
            if (ItemsAdded != null)
            {
                ItemsAdded(sender, e);
            }
        }

        /// <summary>
        /// Raised before an Item is changed to the list.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e">GenericItemEventArgs</param>
        protected virtual void OnBeforeItemChanged(object sender, ItemEventArgs<T> e)
        {
            if (BeforeItemChanged != null)
            {
                BeforeItemChanged(sender, e);
            }
        }

        /// <summary>
        /// Raised when an Item is changed to the list.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e">ItemEventArgs</param>
        protected virtual void OnItemChanged(object sender, ItemEventArgs<T> e)
        {
            if (ItemChanged != null)
            {
                ItemChanged(sender, e);
            }
        }

        /// <summary>
        /// Raised before an Item is removed from the list.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e">ItemEventArgs</param>
        protected virtual void OnBeforeItemRemoved(object sender, ItemEventArgs<T> e)
        {
            if (BeforeItemRemoved != null)
            {
                BeforeItemRemoved(sender, e);
            }
        }

        /// <summary>
        /// Raised when an Item is removed from the list.
        /// </summary>
        /// <param name="sender">object</param>
        /// <param name="e">ItemEventsArgs</param>
        protected virtual void OnItemRemoved(object sender, ItemEventArgs<T> e)
        {
            if (ItemRemoved != null)
            {
                ItemRemoved(sender, e);
            }
        }

        /// <summary>
        /// Raised when the Items are cleared from this list.
        /// </summary>
        /// <param name="sender">object</param>
        /// <param name="e">EventArgs</param>
        protected virtual void OnItemsCleared(object sender, EventArgs e)
        {
            if (ItemsCleared != null)
            {
                ItemsCleared(sender, e);
            }
        }
        #endregion
    }

    public class ItemEventArgs<T> : EventArgs
    {
        /// <summary>
        /// Item
        /// </summary>
        public T Item { get; private set; }

        /// <summary>
        /// Default constructor
        /// </summary>
        /// <param name="Item"></param>
        public ItemEventArgs(T Item)
        {
            this.Item = Item;
        }
    }

    public class ItemsEventArgs<T> : EventArgs
    {
        /// <summary>
        /// Items
        /// </summary>
        public T[] Items { get; private set; }

        /// <summary>
        /// Default constructor
        /// </summary>
        /// <param name="Items"></param>
        public ItemsEventArgs(T[] Items)
        {
            this.Items = Items;
        }
    }
}

Answer 1

我可能错了。但是你可以这样做，你的继承问题就不会出现。我将尝试举一个简单的例子:

你的集合类可能是这样的:

public class MyCollection
    {
        IList<string> MyList { get; set; }

        public event EventHandler<StringEventArgs> OnAdded;
        public event EventHandler<StringEventArgs> OnRemoved;

        public MyCollection()
        {
            MyList = new List<string>();
        }

        public void Add(string s)
        {
            MyList.Add(s);

            if (OnAdded != null)
                OnAdded(this, new StringEventArgs() { StringAddedOrRemoved = s });
        }

        public void Remove(string s)
        {
            MyList.Remove(s);
            if (OnRemoved != null)
                OnRemoved(this, new StringEventArgs() { StringAddedOrRemoved = s });
        }
    }

具有两个自定义事件处理程序的非常简单的类:

public class StringEventArgs : EventArgs
    {
        public string StringAddedOrRemoved;


        public override string ToString()
        {
            return StringAddedOrRemoved;
        }
    }

这里没有什么难理解的，然后基于这三种形式，您可以这样使用您的形式。

第一个包含两个按钮以与集合交互并创建两个将观察您的集合的表单:

public partial class Form1 : Form
    {
        public static MyCollection collection;


        public Form1()
        {

            InitializeComponent();

            collection = new MyCollection();

            Form2 form2 = new Form2();
            form2.Show();

            Form3 form3 = new Form3();
            form3.Show();

            collection.OnAdded += form2.MyCollectionAdded;
            collection.OnRemoved += form2.MyCollectionRemoved;

            collection.OnAdded += form3.MyCollectionAdded;
            collection.OnRemoved += form3.MyCollectionRemoved;

        }

        private void Add_Click(object sender, EventArgs e)
        {
            collection.Add("test add");
        }

        private void button1_Click(object sender, EventArgs e)
        {
            collection.Remove("test add");
        }


    }

该集合链接到将在此处观察到的表单的每个功能:

collection.OnAdded += form2.MyCollectionAdded;
                collection.OnRemoved += form2.MyCollectionRemoved;

                collection.OnAdded += form3.MyCollectionAdded;
                collection.OnRemoved += form3.MyCollectionRemoved;

因此我们需要实现这些表单:

public partial class Form2 : Form
    {


        public string Name { get; set; }
        public bool Flag { get; set; }

        public Form2()
        {
            InitializeComponent();
        }

        public void MyCollectionAdded(object sender, StringEventArgs e)
        {
            //Some action
            Flag = true;
            label1.Text = string.Format("{0} has added {1} to its list, flag={2}", Name, e.StringAddedOrRemoved, Flag);
        }

        public void MyCollectionRemoved(object sender, StringEventArgs e)
        {
            //Some action
            Flag = false;
            label1.Text = string.Format("{0} has removed {1} from its list, flag={2}", Name, e.StringAddedOrRemoved, Flag);
        }
    }

我正在从 Form 继承我的东西，但它可以从任何你想要的形式继承。如果您想在不同的表单之间共享一些代码，请考虑静态类中的辅助函数，或者任何可能适合您需要的模式。

希望它能有所帮助，我并没有完全超出范围!

[EDIT] 哎呀没看到编辑，对不起 friend ![/EDIT]