我也有同样的问题，我必须把我的共享项目转换成一个可移植的类库。

我有同样的问题，期望我把我的主窗口xaml和cs复制到一个新文件，然后把它们复制回原来的地方。在尝试编译WPF应用程序后，我得到了这个错误。

我修复这个错误的方法是重命名命名空间(from egNamespace -> egNamespaceNew)，它再次工作。然后我将名称空间改回原来的名称空间。

在我的案例中(NET Core 3.1)，我通过在项目文件的ProjectGroup部分中给它一个AssemblyName标记来修复它。如。

<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <UseWPF>true</UseWPF>
    <AssemblyName>ProjectNameUsually</AssemblyName>
  </PropertyGroup>
  ...
</Project>

这也修复了编译器在代码背后看不到x:Name控件的问题。

I had a problem similar to this in WPF. I had copied a usercontrol but had forgotten to rename the public ViewModel property in its.xaml.cs file for it. But still wasn't working. I eventually deleted all of the files inside the obj\debug type of folder for the project (we had this named differently). And rebuilt it. It still wasn't working, and I exited Visual Studio. (Before this I had at one point two instances of Visual Studio I think maybe.) The problem I had was that it was reporting it had this error when I had already fixed it! When I came back into Visual Studio (after deleting the debug stuff in obj), there finally was no error indicator. Then I rebuilt the project and now all was good!

这和我之前做的顺序不一样。它需要被简化。

此问题的另一个解决方案是简单地将属性-> Build Action从嵌入式资源更改为其他任何内容，保存，然后将其更改为嵌入式资源。错误消失了。

在我的情况下，程序实例已经在后台运行。我只是停止运行实例和程序构建成功。