用winforms實現觀察者模式

Question

我有一個對象集合，我的許多表單（使用WeifenLuo.WinFormsUI.Docking）都需要與之交互。

即，如果集合以一種形式進行添加（或刪除），則其他形式通過刷新其視圖來響應。

顯然，此處的觀察者模式將是一個不錯的選擇。 但是，我在嘗試在程序中實現此方法時遇到了問題。

首先，最好為我的收藏創​​建一個觀察者類，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) {}
}

然后以子類形式覆蓋基本事件處理程序？

但是，我不能這樣做，只能使用WeifenLuo.WinFormsUI.Docking庫...

好吧，我可以讓DataCollectionObserver從WeifenLuo.WinFormsUI.Docking繼承DockContent，但是這會導致我需要兩個DataCollectionObserver類-一個繼承Form的類，另一個繼承DockContent的類：-[或者，我可以使DataCollectionObserver成為接口，但那仍然給我留下了重復的代碼……

那么，有人在這里有建議嗎？ 我是否遺漏了一些明顯的東西，還是為了簡單起見必須“重復”執行代碼？

---

編輯：//

我在通過表單獲取通知時沒有問題。 事實上，整個事情現在都在起作用。 我要問的原因是，由於代碼的塊復制和粘貼（這是我擁有的這四種不同形式的代碼，它們全都“聞起來”），這些四種形式訂閱了收集事件並在Form.Closing（）上取消訂閱。

我想做的是在一個地方實現復制並粘貼到這四個表單的行為，並讓應該接收集合更改通知的表單根據需要實現該行為。

希望事情變得更清楚嗎？

FWIW，這是我的收藏課：

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

我可能會誤會。 但是您可以通過這種方式進行操作，並且不會出現繼承問題。 我將嘗試舉一個簡單的例子：

您的收集類可能是這種類型：

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 });
        }
    }

具有兩個自定義EventHandlers的非常簡單的類：

public class StringEventArgs : EventArgs
    {
        public string StringAddedOrRemoved;


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

在這里不難理解，然后基於這三種形式，您可以以這種方式使用表單。

第一個包含兩個按鈕以與收藏集進行交互，並創建兩個將觀察收藏集的表單：

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");
        }


    }

該集合鏈接到將在此處觀察到的表單的每個功能：

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

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

因此，我們需要實現這些形式：

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);
        }
    }

我從Form繼承了我的東西，但是無論您想要什么，都可以繼承它。 如果要在不同形式之間共享一些代碼，請考慮靜態類中的輔助函數，或考慮可能適合您需要的任何模式。

希望對您有所幫助，並且我不會完全超出范圍！

[EDIT]糟糕，看不到“編輯”，抱歉，朋友！[/ EDIT]

Answer 2

如果使用的是.net的哪個版本，如果> = 3.5，則可以使用ObservableCollection來實現您正在執行的操作

Answer 3

框架中僅針對此類事物有一個“ ObservableCollection”。 看這里 。