问题描述
本文于 2012 年 8 月发布http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh286406%28v=vs.92%29.aspx，其中讨论了数据库最佳实践.
In august 2012, this article was published http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh286406%28v=vs.92%29.aspx which talks about database best practices.
在本文中，提到必须启用列表框中的数据虚拟化，并建议关注 2010 年 8 月的一篇文章.
In this article, is mentioned that data virtualization in listbox must be enabled and suggests to follow an article dated August 2010.
" 有关在数据绑定 ListBox 控件上启用数据虚拟化的更多信息，请参阅 改进 Silverlight 中的 ListBox 性能 for Windows Phone 7:数据虚拟化"
但是我认为默认情况下启用了 Mango 版本中发布的列表框虚拟化.那是对的吗?绑定到可观察集合的列表框是否默认虚拟化?
However I thought that listbox virtualization is enabled by default with what was released in Mango version.Is that correct? Is a listbox databinded to an observable collection virtualized by default?
推荐答案
默认情况下 Ui 是虚拟化的 - 因此列表框重用列表项的数据模板，并且只呈现那些实际滚动到视图中的列表项.
The Ui is virtualised by default - so the list box reuses datatemplates for the list items, and only renders those list items which are actually scrolled into view.
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但是，如果您使用的是 observablecollection，那么数据不会被虚拟化.
However, if you are using observablecollection, then the data is not virtualised.
因此，如果您有一个包含 1,000,000 个项目的列表，那么所有项目都将在内存中，但只会创建和绘制其中少数项目的 ui.
So if you have a list of 1,000,000 items, then all of them will be in memory, but only the ui for a few of them will be created and drawn.
为了虚拟化数据，您需要实现自定义 ilist，可能还支持 inotifycollectionchanged.例如，此实现可能使用 SQLite 仅在滚动需要时加载数据项.
To virtualise the data as well, you'll need to implement a custom ilist, possibly also supporting inotifycollectionchanged. This implementation might, for example, use SQLite to just load data items as they are needed by scrolling.
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