在 System.Collections.ObjectModel 中找不到 ObservableCollection
两个 WPF 项目，同一台机器，浏览 Collections.ObjectModel
一个有 ObservableCollections 并说
// Type: System.Collections.ObjectModel.ObservableCollection`1
// Assembly: System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
// Assembly location: C:\Program Files\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\Profile\Client\System.dll
另一个（从 3.0 项目升级）没有，并说
// Type: System.Collections.ObjectModel.Collection`1
// Assembly: mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
// Assembly location: C:\Windows\Microsoft.NET\Framework\v2.0.50727\mscorlib.dll
为什么第二个使用 System.Collections.ObjectModel 的引用如此不同？
Two WPF projects, same machine, browse Collections.ObjectModel
one has ObservableCollections and says
// Type: System.Collections.ObjectModel.ObservableCollection`1
// Assembly: System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
// Assembly location: C:\Program Files\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\Profile\Client\System.dll
The other (was upgraded from a 3.0 project,) does not and says
// Type: System.Collections.ObjectModel.Collection`1
// Assembly: mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
// Assembly location: C:\Windows\Microsoft.NET\Framework\v2.0.50727\mscorlib.dll
Why is the second reference to using System.Collections.ObjectModel so different?
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您正在寻找两种不同的类型。不同程序集中的类型可以位于同一命名空间中。
由于升级后的项目不包含对 System.dll 程序集的引用（在 3.0 中它位于 Windowsbase.dll 中），因此它不会具有 ObservableCollection。如果添加对该程序集的引用，您将可以访问该集合。
You are looking at 2 different types. Types in different assemblies can be in the same namespace.
Since your upgraded project doesn't include a reference to the System.dll assembly (in 3.0 it was in Windowsbase.dll), it won't have the ObservableCollection. If you add a reference to that assembly, you will have access to that collection.
查看系统程序集“v4.0\Profile\Client\System.dll”与“Framework\v2.0.50727\mscorlib.dll”的末尾
该项目设置为使用客户端配置文件。进入项目属性并选择完整的 .Net 4 配置文件。
Look at the end of the System assembly "v4.0\Profile\Client\System.dll" vs "Framework\v2.0.50727\mscorlib.dll"
That project is set to use the client profile. Go into project properties and select the full .Net 4 profile instead.
我有多个项目。主项目设置为 .net 4，但引用的项目仍然是 .net 3.5，并且引用 2.0 mscorlib。
I have multiple projects. The main project was set to .net 4 but the referenced project was still .net 3.5 and it was referencing the 2.0 mscorlib.