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：
1: DesignerActionListCollection IWebSmartTasksProvider.GetDesignerActionLists() 2: { 3: DesignerActionListCollection componentActions = null; 4: if (this.Designer != null) 5: { 6: DesignerActionService service = (DesignerActionService) base.DesignerHost.GetService(typeof(DesignerActionService)); 7: if (service != null) 8: { 9: componentActions = service.GetComponentActions(this.Designer.Component); 10: } 11: } 12: if (componentActions == null) 13: { 14: componentActions = new DesignerActionListCollection(); 15: } 16: return componentActions; 17: } 18: 19: 20: 21: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：
1: protected override void GetComponentDesignerActions(IComponent component, DesignerActionListCollection actionLists) 2: { 3: Control control = component as Control; 4: ElementDesigner parent = null; 5: if (control != null) 6: { 7: parent = ElementDesigner.GetElementDesigner(control); 8: } 9: if ((parent == null) || !parent.InTemplateMode) 10: { 11: base.GetComponentDesignerActions(component, actionLists); 12: if ((parent != null) && (parent.Designer != null)) 13: { 14: ControlDesigner designer = parent.Designer as ControlDesigner; 15: if ((designer != null) && (designer.AutoFormats.Count > 0)) 16: { 17: actionLists.Insert(0, new AutoFormatActionList(parent)); 18: } 19: } 20: if ((parent != null) && (parent.Element != null)) 21: { 22: IWebDataFormElementCallback dataFormElementCallback = parent.Element.GetDataFormElementCallback(); 23: if (dataFormElementCallback != null) 24: { 25: DataFormElementActionList list = new DataFormElementActionList(parent, parent.Control, dataFormElementCallback); 26: actionLists.Add(list); 27: DataFormElementActionList.ModifyActionListsForListControl(actionLists, list); 28: } 29: } 30: if (((parent != null) && (parent.Designer != null)) && parent.DocumentDesigner.ExtenderControlHelper.ProvidesActionLists) 31: { 32: parent.DocumentDesigner.ExtenderControlHelper.AddActionLists(parent, actionLists); 33: } 34: } 35: if ((parent != null) && (parent.TemplateEditingUI != null)) 36: { 37: actionLists.Add(new TemplateEditingActionList(parent.TemplateEditingUI, parent.Element)); 38: } 39: } 40: 41: 42: 43:这个方法里，有这么一段：
1: if (((parent != null) && (parent.Designer != null)) && parent.DocumentDesigner.ExtenderControlHelper.ProvidesActionLists) 2: { 3: parent.DocumentDesigner.ExtenderControlHelper.AddActionLists(parent, actionLists); 4: }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：
1: public void AddActionLists(ElementDesigner element, DesignerActionListCollection lists) 2: { 3: lists.Add(new ControlExtenderActionList(element)); 4: ExtenderControl component = element.Designer.Component as ExtenderControl; 5: Control control = element.Designer.Component as Control; 6: if ((component == null) && (control != null)) 7: { 8: IExtenderInformationService service = (IExtenderInformationService) control.Site.GetService(typeof(IExtenderInformationService)); 9: if (service != null) 10: { 11: foreach (Control control3 in service.GetAppliedExtenders(control)) 12: { 13: lists.Add(new HoistedExtenderActionList(element.Designer, control3)); 14: } 15: } 16: } 17: } 18: 19: 20: 21: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：
1: public override DesignerActionItemCollection GetSortedActionItems() 2: { 3: Control component = (Control) this._htmlDesigner.Component; 4: DesignerActionItemCollection items = new DesignerActionItemCollection(); 5: IExtenderInformationService service = (IExtenderInformationService) component.Site.GetService(typeof(IExtenderInformationService)); 6: string category = SR.GetString(SR.Ids.SmartTasksLabelExtenderSection, CultureInfo.CurrentUICulture); 7: if (service.IsControlExtendible(component)) 8: { 9: string displayName = SR.GetString(SR.Ids.SmartTasksAddExtender, CultureInfo.CurrentUICulture); 10: items.Add(new DesignerActionMethodItem(this, "AddExtender", displayName, category, true)); 11: } 12: if (service.IsControlExtended(component)) 13: { 14: string str3 = SR.GetString(SR.Ids.SmartTasksRemoveExtender, CultureInfo.CurrentUICulture); 15: items.Add(new DesignerActionMethodItem(this, "RemoveExtender", str3, category, true)); 16: } 17: return items; 18: } 19: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：
1: protected override void GetComponentDesignerActions(IComponent component, DesignerActionListCollection actionLists) 2: { 3: if (component == null) 4: { 5: throw new ArgumentNullException("component"); 6: } 7: if (actionLists == null) 8: { 9: throw new ArgumentNullException("actionLists"); 10: } 11: IServiceContainer site = component.Site as IServiceContainer; 12: if (site != null) 13: { 14: DesignerCommandSet service = (DesignerCommandSet) site.GetService(typeof(DesignerCommandSet)); 15: if (service != null) 16: { 17: DesignerActionListCollection lists = service.ActionLists; 18: if (lists != null) 19: { 20: actionLists.AddRange(lists); 21: } 22: } 23: if ((actionLists.Count == 0) || ((actionLists.Count == 1) && (actionLists[0] is ControlDesigner.ControlDesignerActionList))) 24: { 25: DesignerVerbCollection verbs = service.Verbs; 26: if ((verbs != null) && (verbs.Count != 0)) 27: { 28: DesignerVerb[] array = new DesignerVerb[verbs.Count]; 29: verbs.CopyTo(array, 0); 30: actionLists.Add(new DesignerActionVerbList(array)); 31: } 32: } 33: } 34: } 35: 36: 37: 38: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：
1: public class MyDesignerCommandSet : DesignerCommandSet 2: { 3: private ComponentDesigner _componentDesigner; 4: 5: public MyDesignerCommandSet(ComponentDesigner componentDesigner) 6: { 7: _componentDesigner = componentDesigner; 8: } 9: 10: public override ICollection GetCommands(string name) 11: { 12: if (name.Equals("ActionLists")) 13: { 14: return GetActionLists(); 15: } 16: return base.GetCommands(name); 17: } 18: 19: private DesignerActionListCollection GetActionLists() 20: { 21: //先取得控件原有的DesignerActionLists 22: DesignerActionListCollection lists = _componentDesigner.ActionLists; 23: 24: //增加“添加动作”这个DesignerActionList 25: lists.Add(new ActionList(_componentDesigner)); 26: return lists; 27: } 28: 29: internal class ActionList : DesignerActionList 30: { 31: private DesignerActionItemCollection _actions; 32: 33: public ActionList(IDesigner designer) 34: : base(designer.Component) 35: { 36: } 37: public override DesignerActionItemCollection GetSortedActionItems() 38: { 39: if (_actions == null) 40: { 41: const string actionCategory = "Actions"; 42: _actions = new DesignerActionItemCollection(); 43: _actions.Add(new DesignerActionMethodItem(this, "AddAction", "添加动作...", actionCategory, true)); 44: } 45: return _actions; 46: } 47: 48: public void AddAction() 49: { 50: //添加动作的逻辑，略 51: } 52: } 53: }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：
1: public class SiteProxy : ISite, IServiceContainer 2: { 3: private ISite _site; 4: private ComponentDesigner _designer; 5: 6: public SiteProxy(ISite site, ComponentDesigner designer) 7: { 8: _site = site; 9: _designer = designer; 10: 11: } 12: 13: #region ISite 成员 14: 15: public IComponent Component 16: { 17: get { return _site.Component; } 18: } 19: 20: public System.ComponentModel.IContainer Container 21: { 22: get { return _site.Container; } 23: } 24: 25: public bool DesignMode 26: { 27: get { return _site.DesignMode; } 28: } 29: 30: public string Name 31: { 32: get { return _site.Name; } 33: set { _site.Name = value; } 34: } 35: 36: #endregion 37: 38: #region IServiceProvider 成员 39: 40: public object GetService(Type serviceType) 41: { 42: object service = _site.GetService(serviceType); 43: 44: if (serviceType == typeof(DesignerCommandSet) && !(_designer.Component is ExtenderControl)) 45: { 46: if (service == null || !(service is MyDesignerCommandSet)) 47: { 48: if (service != null) 49: { 50: RemoveService(typeof(DesignerCommandSet)); 51: } 52: //返回自己写的DesignerCommandSet 53: service = new MyDesignerCommandSet(_designer); 54: AddService(typeof(DesignerCommandSet), service); 55: } 56: } 57: return service; 58: } 59: 60: #endregion 61: 62: #region IServiceContainer 成员 63: 64: public void AddService(Type serviceType, ServiceCreatorCallback callback, bool promote) 65: { 66: (_site as IServiceContainer).AddService(serviceType, callback, promote); 67: } 68: 69: public void AddService(Type serviceType, ServiceCreatorCallback callback) 70: { 71: (_site as IServiceContainer).AddService(serviceType, callback); 72: } 73: 74: public void AddService(Type serviceType, object serviceInstance, bool promote) 75: { 76: (_site as IServiceContainer).AddService(serviceType, serviceInstance, promote); 77: } 78: 79: public void AddService(Type serviceType, object serviceInstance) 80: { 81: (_site as IServiceContainer).AddService(serviceType, serviceInstance); 82: } 83: 84: public void RemoveService(Type serviceType, bool promote) 85: { 86: (_site as IServiceContainer).RemoveService(serviceType, promote); 87: } 88: 89: public void RemoveService(Type serviceType) 90: { 91: (_site as IServiceContainer).RemoveService(serviceType); 92: } 93: 94: #endregion 95: }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：
1: public class ActionManagerDesigner : ControlDesigner 2: { 3: private IDesignerHost _host; 4: private IDictionary<IComponent, ISite> _components; 5: 6: public override void Initialize(IComponent component) 7: { 8: base.Initialize(component); 9: 10: _components = new Dictionary<IComponent, ISite>(); 11: 12: _host = GetService(typeof(IDesignerHost)) as IDesignerHost; 13: if (_host != null) 14: { 15: //替换已有控件的Site 16: ProcessComponent(); 17: 18: IComponentChangeService service = 19: _host.GetService(typeof(IComponentChangeService)) as IComponentChangeService; 20: if (service != null) 21: { 22: service.ComponentAdded += ComponentAdded; 23: service.ComponentRemoving += ComponentRemoving; 24: } 25: } 26: } 27: 28: #region ProcessComponent 29: 30: private void ProcessComponent() 31: { 32: ComponentCollection components = _host.Container.Components; 33: foreach (IComponent component in components) 34: { 35: if (component is ActionControl) 36: continue; 37: ProcessComponentSite(component); 38: } 39: } 40: 41: #endregion 42: 43: #region 替换Site 44: 45: /// <summary> 46: /// 替换Component原来的Site，换成SiteProxy 47: /// </summary> 48: private void ProcessComponentSite(IComponent component) 49: { 50: ComponentDesigner designer = _host.GetDesigner(component) as ComponentDesigner; 51: _components[component] = component.Site; 52: component.Site = new SiteProxy(component.Site, designer); 53: } 54: 55: /// <summary> 56: /// 恢复Component原来的site 57: /// </summary> 58: /// <param name="component"></param> 59: private void RestoreComponentSite(IComponent component) 60: { 61: if (_components.ContainsKey(component)) 62: { 63: ISite site = _components[component]; 64: component.Site = site; 65: _components.Remove(component); 66: } 67: } 68: 69: #endregion 70: 71: #region on Component Add, remove, change 72: 73: private void ComponentRemoving(object sender, ComponentEventArgs e) 74: { 75: if (e.Component is ActionControl) 76: { 77: return; 78: } 79: //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, 80: //这样再添加同名的Component的时候，会报“重复的组件名称”错误 81: RestoreComponentSite(e.Component); 82: } 83: 84: 85: private void ComponentAdded(object sender, ComponentEventArgs e) 86: { 87: if (e.Component is ActionControl) 88: { 89: return; 90: } 91: ProcessComponentSite(e.Component); 92: } 93: 94: #endregion 95: 96: #region dispose 97: 98: protected override void Dispose(bool disposing) 99: { 100: if (_host != null) 101: { 102: IComponentChangeService service = 103: _host.GetService(typeof(IComponentChangeService)) as IComponentChangeService; 104: if (service != null) 105: { 106: service.ComponentAdded -= ComponentAdded; 107: service.ComponentRemoving -= ComponentRemoving; 108: } 109: } 110: base.Dispose(disposing); 111: } 112: 113: #endregion 114: }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。
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