关于网友提出的“动态添加委托失败”问题疑问，本网通过在网上对“动态添加委托失败”有关的相关答案进行了整理，供用户进行参考，详细问题解答如下：
问题：动态添加委托失败
描述:
public class EventWrapper : EventDescriptor
{
object controlledObject;
EventDescriptor controlledEvent;
EventInfo eventInfo;
///
///
///
///
///
public EventWrapper(object controlledObject, EventInfo eventInfo)
: base(eventInfo.GetTargetEventName(), null)
{
this.controlledObject = controlledObject;
this.eventInfo = eventInfo;
foreach (EventDescriptor pd in TypeDescriptor.GetEvents(controlledObject))
{
if (pd.Name == eventInfo.SourceEvent)
{
this.controlledEvent = pd;
break;
}
}
if (this.controlledEvent == null)
throw new System.InvalidOperationException("sourceEvent is not found in controlled object");
}
#region
///
///
///
///
///
public override void AddEventHandler(object component, Delegate value)
{
var ub = UndoRedoManager.GetUndoBufferFor(controlledObject as System.Windows.UIElement);
ub.AddCommand(new ModifyGraphicsObject(controlledObject as System.Windows.UIElement));
//System.Reflection.EventInfo eInfo = ComponentType.GetEvent(Name);
//eInfo.AddEventHandler(controlledObject, value);
controlledEvent.AddEventHandler(controlledObject, value);//这里添加失败怎么回事？
}
///
///
///
///
///
public override void RemoveEventHandler(object component, Delegate value)
{
var ub = UndoRedoManager.GetUndoBufferFor(controlledObject as System.Windows.UIElement);
ub.AddCommand(new ModifyGraphicsObject(controlledObject as System.Windows.UIElement));
controlledEvent.RemoveEventHandler(controlledObject, value);
}
///
///
///
public override Type ComponentType
{
get
{
return controlledEvent.ComponentType;
}
}
///
///
///
public override Type EventType
{
get
{
return controlledEvent.EventType;
}
}
///
///
///
public override bool IsMulticast
{
get { return controlledEvent.IsMulticast; }
}
#endregion
///
///
///
///
///
///
public static bool CheckIfApplicable(object controlledObject, EventInfo eventInfo)
{
foreach (EventDescriptor pd in TypeDescriptor.GetEvents(controlledObject))
{
if (pd.Name == eventInfo.SourceEvent)
return true;
}
return false;
}
///
///
///
public object ControlledObject
{
get { return controlledObject; }
}
///
///
///
public EventDescriptor ControlledEvent
{
get { return controlledEvent; }
}
///
///
///
internal EventInfo EventInfo
{
get { return eventInfo; }
}
///
///
///
public override AttributeCollection Attributes
{
get
{
List attrs = new List();
if (eventInfo.Editor != null && eventInfo.Editor.IsSubclassOf(typeof(System.Drawing.Design.UITypeEditor)))
attrs.Add(new EditorAttribute(eventInfo.Editor, typeof(System.Drawing.Design.UITypeEditor)));
if (string.IsNullOrEmpty(eventInfo.Group) == false)
attrs.Add(new CategoryAttribute(eventInfo.Group));
return new AttributeCollection(attrs.ToArray());
}
}
///
///
///
public override string DisplayName
{
get
{
return eventInfo.GetTargetEventDisplayName();
}
}
///
///
///
public override string Description
{
get
{
if (string.IsNullOrEmpty(eventInfo.Description))
return controlledEvent.Description;
else
return eventInfo.Description;
}
}
///
///
///
public override bool IsBrowsable
{
get
{
return controlledEvent.IsBrowsable;
}
}
///
///
///
public override string Name
{
get
{
return eventInfo.GetTargetEventName();
}
}
///
///
///
///
public override string ToString()
{
return DisplayName;
}
///
///
///
///
public Delegate GetBinding()
{
Delegate[] d = GetObjectEventList(controlledObject, Name, ComponentType);
if (d != null && d.Length > 0)
return d[0];
return null;
}
private Delegate[] GetObjectEventList(object p_Object, string p_EventName, Type p_EventType)
{
PropertyInfo _PropertyInfo = p_Object.GetType().GetProperty("Events", BindingFlags.Instance | BindingFlags.FlattenHierarchy | BindingFlags.IgnoreCase);
PropertyInfo propertyInfo = p_Object.GetType().GetProperty("Events", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.IgnoreCase);
if (_PropertyInfo != null)
{
object _EventList = _PropertyInfo.GetValue(p_Object, null);
if (_EventList != null && _EventList is EventHandlerList)
{
EventHandlerList _List = (EventHandlerList)_EventList;
FieldInfo _FieldInfo = p_EventType.GetField(p_EventName, BindingFlags.Static | BindingFlags.FlattenHierarchy | BindingFlags.IgnoreCase);
if (_FieldInfo == null) return null;
Delegate _ObjectDelegate = _List[_FieldInfo.GetValue(p_Object)];
if (_ObjectDelegate == null) return null;
return _ObjectDelegate.GetInvocationList();
}
}
return null;
}
}
想动态添加委托，重写的AddEventHandler里添加委托失败，怎么回事？
解决方案1: GetEvent("MouseDown");
WPF里没有这个东西
WPF里叫 mouseleftbuttondown
解决方案2: WPF里UIElement采用的都是路由事件
参考
http://www.cnblogs.com/loveis715/archive/2012/04/10/2441513.html
解决方案3:
木有的。控件的基类没提供事件集合。
解决方案4: WPF 里面没有Events 这个你要DEBUG WPF的事件方法是啥，
WPF与WIN下不一样地。
解决方案5: 把代码和现象反复贴出来好几遍,是没有意义的
你先确定这个函数里到底执行到哪就出问题了
如果它一开始就出问题了,你还是重写方法吧
解决方案6: 其实就是Delegate[] GetObjectEventList这东西出问题了呗,放那么多无关代码都是迷惑人的
断点跟,看它到底在哪一句就变成null了
解决方案7: 报的什么错，事件委托和签名跟你传入的handler一致吗
以上介绍了“动态添加委托失败”的问题解答，希望对有需要的网友有所帮助。
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