关于控件事件流程
代码如下:
using   System;
using   System.Collections.Specialized;
using   System.Web.UI;
using   System.Web.UI.WebControls;
using   System.ComponentModel;

namespace   购物车
{
///   <summary>
///   WebCustomControl1   的摘要说明。
///   </summary>
public   enum   LoaderType{DetailLoader,CartLoader};
public   delegate   void   CartLoaderEventHandler(object   sender,CartLoaderEventArgs   e);

public   class   CartLoaderEventArgs:EventArgs
{
private   int   _itemCount;
private   string   _productNumber;

public   CartLoaderEventArgs(){}

public   CartLoaderEventArgs(string   ProductNumber)
{
_itemCount   =   0;
_productNumber   =   ProductNumber;
}

public   CartLoaderEventArgs(string   ProductNumber,int   NumberOfItems)
{
_itemCount   =   NumberOfItems;
_productNumber   =   ProductNumber;
}

public   string   ProductNumber
{
get{return   _productNumber;}
set{_productNumber   =   value;}
}

public   int   NumberOfItems
{
get{return   _itemCount;}
set{_itemCount   =   value;}
}

}

public   class   CartLoader   :   System.Web.UI.WebControls.WebControl,IPostBackDataHandler,IPostBackEventHandler
{
public   event   CartLoaderEventHandler   ItemAdded;
public   event   CartLoaderEventHandler   ItemUpdated;
public   event   CartLoaderEventHandler   ItemRemoved;

private   LoaderType   _location   =   LoaderType.DetailLoader;
private   string   _productID;
private   int   _itemCount;

public   LoaderType   Location
{
get{return   _location;}
set{_location   =   value;}
}
public   string   ProductID
{
get{return   _productID;}
set{_productID   =   value;}
}

public   int   ItemCount
{
get{return   _itemCount;}
set{_itemCount   =   value;}
}

protected   void   OnItemAdded()
{
if(ItemAdded   !=   null)
ItemAdded(this,new   CartLoaderEventArgs(_productID,_itemCount));
}

protected   void   OnItemUpdated()
{
if   (ItemUpdated   !=   null)
ItemUpdated(this,new   CartLoaderEventArgs(_productID,_itemCount));
}

protected   void   OnItemRemoved()
{
if   (ItemRemoved   !=   null)
ItemRemoved(this,new   CartLoaderEventArgs(_productID));
}
//加载文本框数据时引发
public   bool   LoadPostData(string   postDataKey,NameValueCollection   postData)
{
int   count   =   Int32.Parse(postData[postDataKey]);
if   (_itemCount   !=   count)
{
_itemCount   =   count;
return   true;
}
else
{
return   false;
}
}
//如果控件启动回送．也就是有一个按钮被单击．调用此方法
public   void   RaisePostDataChangedEvent()
{
OnItemUpdated();
}

public   void   RaisePostBackEvent(string   eventArgument)
{
if   (eventArgument   ==   "AddToCart ")