这为我解决了问题。

我已经注释掉了App.xaml文件中的资源

<Application x:Class="MyApp.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <Application.Resources>
    <!--<ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary
            Source="/PresentationFramework.Aero, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=MSIL;component/themes/aero.normalcolor.xaml" />
      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>-->
  </Application.Resources>
</Application>

将此注释回来以修复构建错误。

<Application x:Class="MyApp.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <Application.Resources>
    <ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary
            Source="/PresentationFramework.Aero, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=MSIL;component/themes/aero.normalcolor.xaml" />
      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
  </Application.Resources>
</Application>

深入挖掘一下，我发现{Project}\obj\debug中的app.g.cs文件在我留下资源注释时只包含以下内容。

/// <summary>
/// InitializeComponent
/// </summary>
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
public void InitializeComponent() {
    if (_contentLoaded) {
        return;
    }
    _contentLoaded = true;
    System.Uri resourceLocater = new System.Uri("/MyApp;component/app.xaml", System.UriKind.Relative);

    #line 1 "..\..\..\App.xaml"
    System.Windows.Application.LoadComponent(this, resourceLocater);

    #line default
    #line hidden
}

我尝试了上面所有的建议。如果你太努力而没有成功，那就走更容易的路。创建一个新页面。xaml然后复制新类的代码并删除有问题的类xaml。不要花更多的时间。

I know this was answered due to a different cause, but this is a highly hit posting and I had ran into the same issue with a class library. In this case, it turned out to be both a change in my namespace (answered in this post here) and that the compiler could not rebuild the Window.g.i.cs which defines the InitializeComponent() method. It couldn't because the class library was missing the ProjectTypeGuid value for WPF projects in the csproj file. Instructions for this are here and here. I thought I would share in case someone else has run into the same issue. Just changing the namespace isn't enough in this case.

我遇到过几次这种情况，但总是忘记是什么原因造成的。 当我在文件后面的代码上重命名命名空间时，我遇到了这个问题，但不是在XAML中。

所以检查一下你是否做了同样的事情。

名称空间和类名需要匹配，因为它们都是部分类的一部分

namespace ZZZ
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow
    {
         //...
    }
}

<!-- XAML -->
<Window x:Class="ZZZ.MainWindow">

导致这个错误的另一个常见原因是:

Right click on folder in project to create new UserControl. This creates a class and xaml file that derives from user control in the namespace of the folder. Then you decide to change the namespace of the class because you're really just using folders for organization of code. The x:Class attribute will not get automatically updated so it will be searching for a class that doesn't exist. Could probably use a better error message like "x:Class type could not be found in namesace bla.blaa.blaaa."

我同意上面的答案，即名称空间必须匹配。但是，我遇到了这样一个问题，即名称空间匹配。

为了解决这个问题，我简单地将XAML中的名称空间更改为不正确的名称空间，保存，然后将其更改为正确的名称空间。瞧!