资源管理方面的一个陷阱就是说
SPSite和SPWeb
SPSite site=new SPSite("http://localhost");
SPWeb web=site.OpenWeb();
SPWeb web=site.OpenWeb();
相信这两句是每一个写sharepoint开发的人都会写的，可是就在这两句中就有一个大陷阱，是什么呢，就是这两个对象是非托管的对象，是需要明确释放的，释放的两种方式为：
1、using
2、try。。。catch。。。finally。。。
但是呢，有两个意外，那就是
SPSite site= SPContext.Current.Site;
SPWeb web=SPContext.Current.Web;
从SPContext，也就是sharepoint的上下文中获取的这两个对象是托管对象，可以不用显示释放。SPWeb web=SPContext.Current.Web;
二、低效的删除陷阱
SPList list;
foreach(SPListItem item in list.Items)
{
list.Items.DeleteItemById();
}
这一段循环删除lsit中的items，效率很低的，在演示中，删除一条大概要半秒多，大家有兴趣可以尝试一下的。foreach(SPListItem item in list.Items)
{
list.Items.DeleteItemById();
}
那么什么是高效的删除操作呢，就是用
SPWeb web;
web.ProcessBatchData();
spweb中的批处理方法，效率要高300%多呢，详细代码如下：
代码引用自
http://www.cnblogs.com/laputa-sky/archive/2008/10/21/1299867.html
Deleting a large number of items from a list in SharePoint
From :http://blog.thekid.me.uk/archive/2007/02/24/deleting-a-considerable-number-of-items-from-a-list-in-sharepoint.aspx
Recently the question was asked in the newsgroups about deleting a large number of items from SharePoint (WSS) in the fastest way. I had, in one if my projects, needed to remove a large number of item from SharePoint and the best way I found was to use 'ProcessBatchData' as it avoided the API and was considerably faster.
Here is some example code which will remove items from a SharePoint list. If you do this I would remember about the Recycle Bin and the effect deleting many items will have in the future![[引用]编写高质量高效率的SharePoint应用程序](/default/index/img?u=L2RlZmF1bHQvaW5kZXgvaW1nP3U9YUhSMGNITTZMeTkzZDNjdVkyNWliRzluY3k1amIyMHZTVzFoWjJWekwyUnZkQzVuYVdZPQ== "[引用]编写高质量高效率的SharePoint应用程序")
it maybe worth adding some code which also removes the items from the recycle bin once it has finished.
StringBuilder sbDelete = new StringBuilder();
sbDelete.Append("<?xml version=\"1.0\" encoding=\"UTF-8\"?><Batch>");
foreach (SPListItem item in CurrentList.Items)
{
sbDelete.Append("<Method>");
sbDelete.Append("<SetList Scope=\"Request\">" + CurrentList.ID + "</SetList>");
sbDelete.Append("<SetVar Name=\"ID\">" + Convert.ToString(item.ID) + "</SetVar>");
sbDelete.Append("<SetVar Name=\"Cmd\">Delete</SetVar>");
sbDelete.Append("</Method>");
}
sbDelete.Append("</Batch>");
try
{
SPContext.Current.Site.RootWeb.ProcessBatchData(sbDelete.ToString());
}
catch (Exception ex)
{
Console.WriteLine("Delete failed: " + ex.Message);
throw;
}
I took me some time to re-find this code and so I have posted it here more for my benefit, but if anyone finds it useful then great.
三、低效的查询，From :http://blog.thekid.me.uk/archive/2007/02/24/deleting-a-considerable-number-of-items-from-a-list-in-sharepoint.aspx
Recently the question was asked in the newsgroups about deleting a large number of items from SharePoint (WSS) in the fastest way. I had, in one if my projects, needed to remove a large number of item from SharePoint and the best way I found was to use 'ProcessBatchData' as it avoided the API and was considerably faster.
Here is some example code which will remove items from a SharePoint list. If you do this I would remember about the Recycle Bin and the effect deleting many items will have in the future
StringBuilder sbDelete = new StringBuilder();
sbDelete.Append("<?xml version=\"1.0\" encoding=\"UTF-8\"?><Batch>");
foreach (SPListItem item in CurrentList.Items)
{
sbDelete.Append("<Method>");
sbDelete.Append("<SetList Scope=\"Request\">" + CurrentList.ID + "</SetList>");
sbDelete.Append("<SetVar Name=\"ID\">" + Convert.ToString(item.ID) + "</SetVar>");
sbDelete.Append("<SetVar Name=\"Cmd\">Delete</SetVar>");
sbDelete.Append("</Method>");
}
sbDelete.Append("</Batch>");
try
{
SPContext.Current.Site.RootWeb.ProcessBatchData(sbDelete.ToString());
}
catch (Exception ex)
{
Console.WriteLine("Delete failed: " + ex.Message);
throw;
}
I took me some time to re-find this code and so I have posted it here more for my benefit, but if anyone finds it useful then great.
SPList list;
foreach(SPListItem item in list.Items)
{
if(item["name"]=="virus")
{
Console.WriteLine("yes");
}
}
像这样的循环查找，除非你的列表中只有很少的记录，要不就使用SPQuery，上面的做法会导致返回全部的对象，所有效率很低，有时候效率低，不是因为sharepoint本身的问题，而是我们选择了错误的方法。
SPQuery的最大缺陷就是不支持联合查询，也就是sql中的join，不知道下一个版本会不会实现这个很好用的功能呢。
四、得到list的item的数量
可能我们都习惯了
list.Items.Count
这样的效率也是非常低下的，因为他会返回alllitem，这是设计问题，但是微软提供了
list.ItemCount;
这个属性同样是返回count，但是却没有了上面的问题，建议大家使用。
还有啊，这个版本还有一个2000限制，就是说一个应用最好不要超过2000个网站，一个网站不要最好超过2000个列表，一个列表下面最好不要超过2000个item，超过之后性能会急剧下降，但是不是致命的，超过2000，微软建议建立文件夹来分类存放，当前版本的列表也支持文件夹了吗。
另外的一节课是候钟雷和杜伟的自定义列的开发，主要的意义还在于扩展了我们的开发思路，列不仅仅是一个单行文本或者日期输入之类的东西了，而是可以看做一个对象，然后这个对象又是一个复杂的输入。
比如说在场地订阅功能中，自定义一个冲突检测列，就是一个验证函数，用来验证场地的订阅日期和已经存在的时间有无冲突。还可以表现一个主子表的内容，就是说可以是一个SPGridView控件，来显示详细表的内容，然后还可以编辑。微软的权限可以控制到条目级，但是列可以定义是否可以，是否可以编辑，估计下一版会丰富到栏目级吧。