实现类似“添加扩展程序…”的设计时支持

    Ajax Control Toolkit这个控件库内包含一些扩展控件，利用这些扩展控件，可以非常方便的为普通的控件添加Ajax效果，例如，利用AutoCompleteExtender控件，可以为文本框添加自动完成的ajax效果。当然，这并不是本文想讨论的内容。

    将Ajax Control Toolkit加入到Visual Studio 2008的工具箱中，并打开一个新的aspx文件，向里面拖入一个TextBox。这时，有趣的事情发生了，在TextBox的SmartTasks面板里，竟然出现了一个“添加扩展程序…”的链接！我又试着拖入一个Button，一个Panel，无一例外的，每个控件的SmartTasks面板的底部都出现了“添加扩展程序…”的链接。

    最近我正打算把保存、删除、关闭页面等功能抽象成动作，每一种动作对应一个自定义的Web控件，将某个动作控件附加到目标控件（例如Button）上面之后，目标控件就拥有了诸如保存、删除、关闭页面的功能。如何在WebForm设计器里为一个Button控件方便地附加动作？我想要的正是类似“添加扩展程序…”这样的效果。

    开发过自定义服务器控件的朋友应该知道，如果想给控件添加SmartTasks，需要重写ControlDesigner的ActionLists属性，并实现自己的DesignerActionList。显然，一个TextBox并不知道AjaxControlToolkit的存在，所以“添加扩展程序…”这么一个DesignerActionMethodItem并不是它加进来的。那么，.net framework是否提供了某种接口，可以让我们为别的控件“动态的注入”DesignerActionItem呢？

    通过对AjaxControlToolKit.dll的研究，我发现这些扩展控件的Designer并不负责提供“添加扩展程序”这个Action，他们只负责提供相应扩展程序对应的扩展内容，所以只能从Visual studio的webform designer作为入口来研究。用reflector打开Microsoft Visual Studio 9.0\Common7\IDE\Microsoft.Web.Design.Client.dll，找到了IWebSmartTasksProvider接口，该接口有一个GetDesignerActionLists的方法，这个方法的返回值应该就是SmartTasks面板里显示的内容了。这个接口有3个实现类，DataFormDesigner、DataFormXslValueOfDesigner、ElementDesigner。从这三个类的命名上可以推断，ElementDesigner应该是用的最多的实现类了。ElementDesigner的GetDesignerActionLists的方法实现如下：

DesignerActionListCollection IWebSmartTasksProvider.GetDesignerActionLists()
{
    DesignerActionListCollection componentActions = null;
    if (this.Designer != null)
    {
        DesignerActionService service = (DesignerActionService) base.DesignerHost.GetService(typeof(DesignerActionService));
        if (service != null)
        {
            componentActions = service.GetComponentActions(this.Designer.Component);
        }
    }
    if (componentActions == null)
    {
        componentActions = new DesignerActionListCollection();
    }
    return componentActions;
}

    从上面代码里可以看到最终的DesignerActionListCollection是由System.Design程序集下的System.ComponentModel.Design.DesignerActionService类的GetComponentActions决定的，Microsoft.Web.Design.Client.dll下的Microsoft.Web.Design.WebFormDesigner+WebDesignerActionService继承了该类，他的实现如下：

protected override void GetComponentDesignerActions(IComponent component, DesignerActionListCollection actionLists)
{
    Control control = component as Control;
    ElementDesigner parent = null;
    if (control != null)
    {
        parent = ElementDesigner.GetElementDesigner(control);
    }
    if ((parent == null) || !parent.InTemplateMode)
    {
        base.GetComponentDesignerActions(component, actionLists);
        if ((parent != null) && (parent.Designer != null))
        {
            ControlDesigner designer = parent.Designer as ControlDesigner;
            if ((designer != null) && (designer.AutoFormats.Count > 0))
            {
                actionLists.Insert(0, new AutoFormatActionList(parent));
            }
        }
        if ((parent != null) && (parent.Element != null))
        {
            IWebDataFormElementCallback dataFormElementCallback = parent.Element.GetDataFormElementCallback();
            if (dataFormElementCallback != null)
            {
                DataFormElementActionList list = new DataFormElementActionList(parent, parent.Control, dataFormElementCallback);
                actionLists.Add(list);
                DataFormElementActionList.ModifyActionListsForListControl(actionLists, list);
            }
        }
        if (((parent != null) && (parent.Designer != null)) && parent.DocumentDesigner.ExtenderControlHelper.ProvidesActionLists)
        {
            parent.DocumentDesigner.ExtenderControlHelper.AddActionLists(parent, actionLists);
        }
    }
    if ((parent != null) && (parent.TemplateEditingUI != null))
    {
        actionLists.Add(new TemplateEditingActionList(parent.TemplateEditingUI, parent.Element));
    }
}

    这个方法里，有这么一段：

if (((parent != null) && (parent.Designer != null)) && parent.DocumentDesigner.ExtenderControlHelper.ProvidesActionLists)
       {
           parent.DocumentDesigner.ExtenderControlHelper.AddActionLists(parent, actionLists);
       }

    看来“添加扩展程序”这个action就是在这里加进去的了。继续查看ExtenderControlHelper.AddActionLists的实现：

public void AddActionLists(ElementDesigner element, DesignerActionListCollection lists)
{
    lists.Add(new ControlExtenderActionList(element));
    ExtenderControl component = element.Designer.Component as ExtenderControl;
    Control control = element.Designer.Component as Control;
    if ((component == null) && (control != null))
    {
        IExtenderInformationService service = (IExtenderInformationService) control.Site.GetService(typeof(IExtenderInformationService));
        if (service != null)
        {
            foreach (Control control3 in service.GetAppliedExtenders(control))
            {
                lists.Add(new HoistedExtenderActionList(element.Designer, control3));
            }
        }
    }
}

    这个方法里的第一句是lists.Add(new ControlExtenderActionList(element))，ControlExtenderActionList继承了System.ComponentModel.Design.DesignerActionList，他的GetSortedActionItems方法定义如下：

public override DesignerActionItemCollection GetSortedActionItems()
{
    Control component = (Control) this._htmlDesigner.Component;
    DesignerActionItemCollection items = new DesignerActionItemCollection();
    IExtenderInformationService service = (IExtenderInformationService) component.Site.GetService(typeof(IExtenderInformationService));
    string category = SR.GetString(SR.Ids.SmartTasksLabelExtenderSection, CultureInfo.CurrentUICulture);
    if (service.IsControlExtendible(component))
    {
        string displayName = SR.GetString(SR.Ids.SmartTasksAddExtender, CultureInfo.CurrentUICulture);
        items.Add(new DesignerActionMethodItem(this, "AddExtender", displayName, category, true));
    }
    if (service.IsControlExtended(component))
    {
        string str3 = SR.GetString(SR.Ids.SmartTasksRemoveExtender, CultureInfo.CurrentUICulture);
        items.Add(new DesignerActionMethodItem(this, "RemoveExtender", str3, category, true));
    }
    return items;
}

    这下清楚了，“添加扩展程序”这个action，是在Visual studio的web form设计器里，写死进去的，.net framework并没有提供相应接口来供我们添加类似的action。但是我想要的效果是增加一个“添加动作”的action，所以我不能参考AjaxControlToolkit的方法去实现，应该要寻找别的方法。

    回过头来，重新查看Microsoft.Web.Design.WebFormDesigner+WebDesignerActionService类的GetComponentActions方法，找到基类System.Web.UI.Design.WebFormsDesignerActionService（在System.Design程序集下）的定义，如下：

protected override void GetComponentDesignerActions(IComponent component, DesignerActionListCollection actionLists)
{
    if (component == null)
    {
        throw new ArgumentNullException("component");
    }
    if (actionLists == null)
    {
        throw new ArgumentNullException("actionLists");
    }
    IServiceContainer site = component.Site as IServiceContainer;
    if (site != null)
    {
        DesignerCommandSet service = (DesignerCommandSet) site.GetService(typeof(DesignerCommandSet));
        if (service != null)
        {
            DesignerActionListCollection lists = service.ActionLists;
            if (lists != null)
            {
                actionLists.AddRange(lists);
            }
        }
        if ((actionLists.Count == 0) || ((actionLists.Count == 1) && (actionLists[0] is ControlDesigner.ControlDesignerActionList)))
        {
            DesignerVerbCollection verbs = service.Verbs;
            if ((verbs != null) && (verbs.Count != 0))
            {
                DesignerVerb[] array = new DesignerVerb[verbs.Count];
                verbs.CopyTo(array, 0);
                actionLists.Add(new DesignerActionVerbList(array));
            }
        }
    }
}

    通过研究上述代码，可以看到DesignerActionListCollection是由DesignerCommandSet这个service的ActionLists属性负责返回的，而这个service是从component的Site里面取得的，只要我另外写一个DesignerCommandSet，并且保证从Site里面取出的DesignerCommandSet是我写的这个service就可以了。终于找到了切入点，下面是具体做法。

    首先，创建一个类继承DesignerCommandSet，如下：

public class MyDesignerCommandSet : DesignerCommandSet
    {
        private ComponentDesigner _componentDesigner;

        public MyDesignerCommandSet(ComponentDesigner componentDesigner)
        {
            _componentDesigner = componentDesigner;
        }

        public override ICollection GetCommands(string name)
        {
            if (name.Equals("ActionLists"))
            {
                return GetActionLists();
            }
            return base.GetCommands(name);
        }

        private DesignerActionListCollection GetActionLists()
        {
            //先取得控件原有的DesignerActionLists
            DesignerActionListCollection lists = _componentDesigner.ActionLists;

            //增加“添加动作”这个DesignerActionList
            lists.Add(new ActionList(_componentDesigner));
            return lists;
        }

        internal class ActionList : DesignerActionList
        {
            private DesignerActionItemCollection _actions;

            public ActionList(IDesigner designer)
                : base(designer.Component)
            {
            }
            public override DesignerActionItemCollection GetSortedActionItems()
            {
                if (_actions == null)
                {
                    const string actionCategory = "Actions";
                    _actions = new DesignerActionItemCollection();
                    _actions.Add(new DesignerActionMethodItem(this, "AddAction", "添加动作...", actionCategory, true));
                }
                return _actions;
            }

            public void AddAction()
            {
                //添加动作的逻辑，略
            }
        }
    }

    下一步就是如何使component的Site这个ServiceProvider返回自己的这个service。方法是自己写一个Site，并使Component的Site变成自己写的SIte类的对象。

    自己写的Site类的定义如下：

public class SiteProxy : ISite, IServiceContainer
    {
        private ISite _site;
        private ComponentDesigner _designer;

        public SiteProxy(ISite site, ComponentDesigner designer)
        {
            _site = site;
            _designer = designer;

        }

        #region ISite 成员

        public IComponent Component
        {
            get { return _site.Component; }
        }

        public System.ComponentModel.IContainer Container
        {
            get { return _site.Container; }
        }

        public bool DesignMode
        {
            get { return _site.DesignMode; }
        }

        public string Name
        {
            get { return _site.Name; }
            set { _site.Name = value; }
        }

        #endregion

        #region IServiceProvider 成员

        public object GetService(Type serviceType)
        {
            object service = _site.GetService(serviceType);

            if (serviceType == typeof(DesignerCommandSet) && !(_designer.Component is ExtenderControl))
            {
                if (service == null || !(service is MyDesignerCommandSet))
                {
                    if (service != null)
                    {
                        RemoveService(typeof(DesignerCommandSet));
                    }
                    //返回自己写的DesignerCommandSet
                    service = new MyDesignerCommandSet(_designer);
                    AddService(typeof(DesignerCommandSet), service);
                }
            }
            return service;
        }

        #endregion

        #region IServiceContainer 成员

        public void AddService(Type serviceType, ServiceCreatorCallback callback, bool promote)
        {
            (_site as IServiceContainer).AddService(serviceType, callback, promote);
        }

        public void AddService(Type serviceType, ServiceCreatorCallback callback)
        {
            (_site as IServiceContainer).AddService(serviceType, callback);
        }

        public void AddService(Type serviceType, object serviceInstance, bool promote)
        {
            (_site as IServiceContainer).AddService(serviceType, serviceInstance, promote);
        }

        public void AddService(Type serviceType, object serviceInstance)
        {
            (_site as IServiceContainer).AddService(serviceType, serviceInstance);
        }

        public void RemoveService(Type serviceType, bool promote)
        {
            (_site as IServiceContainer).RemoveService(serviceType, promote);
        }

        public void RemoveService(Type serviceType)
        {
            (_site as IServiceContainer).RemoveService(serviceType);
        }

        #endregion
    }

    在这个Site的GetService方法中，判断要get的service类型，如果是DesignerCommandSet，就返回自己创建的MyDesignerCommandSet。

    下一步是如何使component的Site变成自己写的SiteProxy。一种方法是新增一种自定义控件，在该控件的ControlDesigner的Initialize方法中改变Container中其他控件的Site，只需要向WebForm中拖入该控件，就可以改变其他控件的Site；另外一种方法是写一个vs package，在package中捕获web form designer的相应事件。下面介绍第一种做法：

    新增一个继承自Control的控件，叫做ActionManager，这个控件不用添加任何功能，只需要为它制作ControlDesigner。它的ControlDesigner类主要代码如下：

public class ActionManagerDesigner : ControlDesigner
    {
        private IDesignerHost _host;
        private IDictionary<IComponent, ISite> _components;

        public override void Initialize(IComponent component)
        {
            base.Initialize(component);

            _components = new Dictionary<IComponent, ISite>();

            _host = GetService(typeof(IDesignerHost)) as IDesignerHost;
            if (_host != null)
            {
                //替换已有控件的Site
                ProcessComponent();

                IComponentChangeService service =
                    _host.GetService(typeof(IComponentChangeService)) as IComponentChangeService;
                if (service != null)
                {
                    service.ComponentAdded += ComponentAdded;
                    service.ComponentRemoving += ComponentRemoving;
                }
            }
        }

        #region ProcessComponent

        private void ProcessComponent()
        {
            ComponentCollection components = _host.Container.Components;
            foreach (IComponent component in components)
            {
                if (component is ActionControl)
                    continue;
                ProcessComponentSite(component);
            }
        }

        #endregion

        #region 替换Site

        /// <summary>
        /// 替换Component原来的Site，换成SiteProxy
        /// </summary>
        private void ProcessComponentSite(IComponent component)
        {
            ComponentDesigner designer = _host.GetDesigner(component) as ComponentDesigner;
            _components[component] = component.Site;
            component.Site = new SiteProxy(component.Site, designer);
        }

        /// <summary>
        /// 恢复Component原来的site
        /// </summary>
        /// <param name="component"></param>
        private void RestoreComponentSite(IComponent component)
        {
            if (_components.ContainsKey(component))
            {
                ISite site = _components[component];
                component.Site = site;
                _components.Remove(component);
            }
        }

        #endregion

        #region on Component Add, remove, change

        private void ComponentRemoving(object sender, ComponentEventArgs e)
        {
            if (e.Component is ActionControl)
            {
                return;
            }
            //在删除Component的时候，要把他的Site属性还原回去，否则DesignerHost中还会保留原来的Site,
            //这样再添加同名的Component的时候，会报“重复的组件名称”错误
            RestoreComponentSite(e.Component);
        }


        private void ComponentAdded(object sender, ComponentEventArgs e)
        {
            if (e.Component is ActionControl)
            {
                return;
            }
            ProcessComponentSite(e.Component);
        }

        #endregion

        #region dispose

        protected override void Dispose(bool disposing)
        {
            if (_host != null)
            {
                IComponentChangeService service =
                    _host.GetService(typeof(IComponentChangeService)) as IComponentChangeService;
                if (service != null)
                {
                    service.ComponentAdded -= ComponentAdded;
                    service.ComponentRemoving -= ComponentRemoving;
                }
            }
            base.Dispose(disposing);
        }

        #endregion
    }

   至此，只要把一个ActionManager控件拖入到web form designer中，就可以在其他控件的smart task面板上看到“添加动作…”这个链接了。但是这种方式需要在webform designer中放入额外的一个控件，该控件只在设计时有用，在运行时则无用，看起来比较奇怪，所以最好的做法是第二种做法，即开发一个vs package，在package的Initialize方法中，注册IDesignerEventService的DesignerCreated事件，进而通过IDesignerHost和IComponentChangeService达到更改控件Site的目的，具体实现和上面差不多，就不再写了。