过滤对象 ObservableCollection

发布于 2024-11-18 23:15:24 字数 885 浏览 2 评论 0原文

我有一个 ObservableCollection

我有以下代码，但不起作用：

var files = (from File f in (from Directory d in selectedDirs
                             select d.Childs)
             where f is File
             select f);

我收到此错误：

无法转换类型的对象 'System.Collections.ObjectModel.ObservableCollection`1[System.Object]' 输入“CMBraga_FileExplorer.File”。

我怎样才能得到我的价值观？我知道它们是File。

// this was ran without explicit conversion ( just as an example )

? myCollection
Count = 5
    [0]: {CMBraga_FileExplorer.File}
    [1]: {CMBraga_FileExplorer.File}
    [2]: {CMBraga_FileExplorer.File}
    [3]: {CMBraga_FileExplorer.File}
    [4]: {CMBraga_FileExplorer.File}

原文

I have a ObservableCollection<Object> that holds two different types of objects: Directory and File. This collection is bound to a control and at some time, I want to filter out the Files.

I have the following code, which is not working:

var files = (from File f in (from Directory d in selectedDirs
                             select d.Childs)
             where f is File
             select f);

I'm getting this error:

Unable to cast object of type
'System.Collections.ObjectModel.ObservableCollection`1[System.Object]'
to type 'CMBraga_FileExplorer.File'.

How can I get my values? I know they are Files.

// this was ran without explicit conversion ( just as an example )

? myCollection
Count = 5
    [0]: {CMBraga_FileExplorer.File}
    [1]: {CMBraga_FileExplorer.File}
    [2]: {CMBraga_FileExplorer.File}
    [3]: {CMBraga_FileExplorer.File}
    [4]: {CMBraga_FileExplorer.File}

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百合的盛世恋 2024-11-25 23:15:24

我怀疑您收到异常的原因是因为您声明了查询变量的类型（即 from File f in ...）。通过这样做，您正在尝试将对象转换为指定的类型。看起来 d.Childs 中某些项目的类型是 ObservableCollection

使用 Enumerable.OfType() 扩展这里的方法进行过滤。这正是它的用途。

var files = selectedDirs
    .Cast<Directory>() // this cast might not even be necessary
    .SelectMany(d => d.Childs)
    .OfType<File>(); // filter selecting only File objects

I suspect the reason you're getting the exception is because you are declaring the types of your query variable (i.e., from File f in ...). By doing that, you are trying to cast the objects to the specified type. It would appear that your types of some of the items in d.Childs are ObservableCollection<Object>. Those are clearly not File objects hence the cast error.

Use the Enumerable.OfType() extension method here to do the filtering. This is exactly what it was made for.

var files = selectedDirs
    .Cast<Directory>() // this cast might not even be necessary
    .SelectMany(d => d.Childs)
    .OfType<File>(); // filter selecting only File objects

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简单爱 2024-11-25 23:15:24

您可以使用 Linq 表达式：

using System.Linq;
// ...
ObservableCollection<object> list;
// ...
IEnumerable<CMBraga_FileExplorer.File> castedList = list.Cast<CMBraga_FileExplorer.File>();

You can use Linq expression for that:

using System.Linq;
// ...
ObservableCollection<object> list;
// ...
IEnumerable<CMBraga_FileExplorer.File> castedList = list.Cast<CMBraga_FileExplorer.File>();

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