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>Update操作中间的时间，数据源的连接是断开的，你能够随便的使用DataSet对数据进行读写。这些是使用断开数据的机制。因为只有当需要的时候应用程序才连接，这样应用程序才更加的可扩展。
A couple scenarios illustrate why you would want to work with disconnected data: people working without network connectivity and making Web sites more scalable. Consider sales people who need customer data as they travel. At the beginning of the day, they''''ll need to sync up with the main data base to have the latest information available. During the day, they''''ll make modifications to existing customer data, add new customers, and input new orders. This is okay because they have a given region or customer base where other people won''''t be changing the same records. At the end of the day, the sales person will connect to the network and update changes for overnight processing.
一对场景描述了为什么你需要断开数据：人们使用网络连接并使web站点更加可扩展。考虑销售人员在旅行的时候需要客户数据。在最初的几天，他们将需要与主数据库同步以获得有效的最新信息。在这些天，它们将对已存在的用户数据进行修改，添加年用户，并且添加新的订单。这都是可以的，因为他们有相应的地区或者客户基础，而其它的用户不会改变相同的记录。在最后的几天中，销售人员将连接网络并把前晚上的改变的数据更新。
Another scenario is making a Web site more scalable. With a SqlDataReader, you have to go back to the data base for records every time you show a page. This requires a new connection for each page load, which will hurt scalability as the number of users increase. One way to relieve this is to use a DataSet that is updated one time and stored in cache. Every request for the page checks the cache and loads the data if it isn''''t there or just pulls the data out of cache and displays it. This avoids a trip to the data base, making your application more efficient.
另一个场景是使web站点更加可扩展。使用SqlDataReader，你必须在显示每一页的时候返回数据库读取记录。则需要对每一次页面装载重新读取数据库，这将在用户数量增加的时候引起麻烦。消除这种情况的一种办法是使用DataSet，它只更新一次并缓存数据。每一个对页面的查询都会检测缓存并显示它。这避免的数据库的连接，使你的应用程序更加有效率。
Exceptions to the scenario above include situations where you need to update data. You then have to make a decision, based on the nature of how the data will be used as to your strategy. Use disconnected data when your information is primarily read only, but consider other alternatives (such as using SqlCommand object for immediate update) when your requirements call for something more dynamic. Also, if the amount of data is so large that holding it in memory is impractical, you will need to use SqlDataReader for read-only data. Really, one could come up with all kinds of exceptions, but the true guiding force should be the requirements of your application which will influence what your design should be.
上面的场景的异常包括你需要更新数据的情况。你必须抉择，基于你的场景中的数据如何被使用。当你的信息主要是读，则使用断开数据，但是当你需要更加动态的调用某些东西的时候，考虑其它的可选项（比如使用SqlCommand对象直接更新）。实际上，万事难料，但真正的指导方针应该是应用程序的需求，它将影响你的设计。
Creating a DataSet Object
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[Web开发]ADO.NET读书笔记系列之------SqlDataAdapter对象
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