使用异步调用进行分层数据检索和显示的模式？
上下文 Silverlight/WPF、C#、.NET 4，
我有一个 4 级深的缩略图树，我需要以某种有意义的方式枚举和显示。 对于同步执行（顺序世界），我们可以这样思考
Channels = Channels_Build("CHANNELS.XML");
foreach Ch in Channels
{
Cats = Cats_Build( Ch.URL ) ;
foreach Cat in Cats
{
PLs = PLs_Build( Cat.URL ) ;
foreach PL in PLs
{
Medias = Medias_Build( PL.URL ) ;
foreach Media in Medias
display Media image
}
}
}
： 然而，我有一个用于 XML、图像等的异步加载模型，所以我想的是这样的：
Channels_Build("CHANNELS.XML");
Channels_Loaded()
{ // Channels build from some returned XML
foreach Ch in Channels
Cats_Build( Ch.URL, ??? ) ; //async calls
}
Cats_Loaded()
{ // Cats build from some returned XML
foreach Cat in Cats
PLs_Build( Cat.URL ... ) ;
}
PLs_Loaded()
{ // PLs build from some returned XML
foreach PL in PLs
MediaList_Build( PL.URL ... ) ;
}
MediaList_Loaded()
{ // MediaList build from some returned XML
foreach media in MediaList
display Media image
}
每个 Channels_Build、Cats_Build、PLs_Build、MediaList_Build 都会进行异步调用，因此有一个关联的回调 xxx_Loaded()
每个 Channel 有 1或更多类别。 每个类别有 1 个或多个播放列表。 每个播放列表有 1 个或多个媒体 因此，我有一个 4 层深的层次结构
。您可以假设 Channels、Cats、PL 和 MediaList 共享一个公共基类。
我应该将这个 4x 逻辑折叠到单个递归构建方法中吗？如何？我必须让构建过程将一些信息（父节点）传递给其相应的回调（我查找了 IAsyncResult.AsyncState）
我的大脑被锁定了，我想不出这里需要什么？递归？，将信息传递给异步调用，特定模式？，...
我应该首先将内存中的树数据构建到一个结构中吗？或者只有当我决定使用 TreeView 控件时才有用？例如，如果我决定使用重复模板将信息显示到列表框中，该怎么办？模板将显示：
Channel-Image+Name
Category-Image+Name
PlayList-Image+Name
MediaList images...
是的，非叶节点将在列表中视觉上重复。这很好，因为它可能会提供我正在寻找的地图。
所以令人困惑的问题仍然存在： 如何枚举并显示此异步模型中的所有节点？
谢谢。
Context Silverlight/WPF, C#, .NET 4,
I have a 4 level deep tree of thumbnails I need to enumerate and display in some meaningful way.
For a Synchronous execution (sequential world) we could think like the following:
Channels = Channels_Build("CHANNELS.XML");
foreach Ch in Channels
{
Cats = Cats_Build( Ch.URL ) ;
foreach Cat in Cats
{
PLs = PLs_Build( Cat.URL ) ;
foreach PL in PLs
{
Medias = Medias_Build( PL.URL ) ;
foreach Media in Medias
display Media image
}
}
}
.
However I have an Async loading model for XML, images, ..., so I am thinking something like this:
Channels_Build("CHANNELS.XML");
Channels_Loaded()
{ // Channels build from some returned XML
foreach Ch in Channels
Cats_Build( Ch.URL, ??? ) ; //async calls
}
Cats_Loaded()
{ // Cats build from some returned XML
foreach Cat in Cats
PLs_Build( Cat.URL ... ) ;
}
PLs_Loaded()
{ // PLs build from some returned XML
foreach PL in PLs
MediaList_Build( PL.URL ... ) ;
}
MediaList_Loaded()
{ // MediaList build from some returned XML
foreach media in MediaList
display Media image
}
Each of Channels_Build, Cats_Build, PLs_Build, MediaList_Build make an Async call and thus have an associated callback xxx_Loaded()
Each Channel has 1 or more Categories.
Each Category has 1 or more PlayLists.
Each PlayList has 1 or more Media
Thus, I have a 4 levels deep hierarchical structure
You can assume Channels, Cats, PLs and MediaList share a common base class.
Should I fold this 4x logic into a single recursive build method? How? I would have to make the build process pass some info (parent node) to its corresponding callback (I looked up IAsyncResult.AsyncState)
My brain is locked up and I can't think of what's needed here? recursion?, passing info to Async calls, specific pattern?, ...
Should I build the tree data in memory, into one structure, first? or would that be useful only if I decide to use a TreeView control? What if I decide to display the info using a repeating template into a listbox for example. The template would display:
Channel-Image+Name
Category-Image+Name
PlayList-Image+Name
MediaList images...
Yes, the non-leaf nodes would repeat visually down the list. That's fine as it might provide the map I am looking for.
So the puzzling question remains:
How do I go about enumerating and displaying all the nodes in this Async model?
Thank you.
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我会看看异步 CTP 刷新，它可以大大简化这些事情
I would look at Async CTP refresh that simplifies this stuff a lot