.xaml文件的构建动作也必须设置为“Page”，当在项目之间移动xaml文件时，这个设置会丢失(至少在VS 2010中是这样)。

我在重命名用户控件时遇到了这个问题。我修复它的方法是注释掉InitializeComponent，验证所有名称都是正确的(xaml和后面的代码)，构建项目，取消InitializeComponent的注释，然后再次构建。听起来这个问题可能有几个原因/解决方案，但这种方法对我来说很管用。

在一些操作之后，.cs文件的命名空间和。xaml文件中的命名空间可能是不同的(在xaml中查找x:Class="namespace. yourtype ")。

使它们相同。

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。

当我试图构建一个针对net48的SDK项目时，这种情况发生在我身上。它与MSBuild.exe一起工作很好，但dotnet构建失败与给定的错误。

对我有用的是

在<PropertyGroup/>节点中添加<UseWPF>true</UseWPF> 删除所有<Page />元素，因为它们现在已被自动包含。

现在msbuild和dotnet都可以构建了。

以下是完整的项目文件:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
    <ProjectGuid>{07465991-AC74-4C22-B1DE-7BA67A040631}</ProjectGuid>
    <OutputType>library</OutputType>
    <RootNamespace>MyRootNamespace</RootNamespace>
    <AssemblyName>MyAssemblyName</AssemblyName>
    <FileAlignment>512</FileAlignment>
    <PackagesDirectory>$(UserProfile)\.nuget\packages</PackagesDirectory>
    <ResolveNuGetPackages>true</ResolveNuGetPackages>
    <SkipValidatePackageReferences>true</SkipValidatePackageReferences>
    <TargetFramework>net48</TargetFramework>
    <TargetFrameworkProfile />
    <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
    <IsNetCoreProject>false</IsNetCoreProject>
    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">15.0</VisualStudioVersion>
    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
    <AutoGenerateBindingRedirect>true</AutoGenerateBindingRedirect>
    <ResolveAssemblyReferencesSilent>true</ResolveAssemblyReferencesSilent>
    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
    <UseWPF>true</UseWPF>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
    <DebugSymbols>true</DebugSymbols>
    <DebugType>embedded</DebugType>
    <Optimize>false</Optimize>
    <OutputPath>bin\</OutputPath>
    <DefineConstants>DEBUG;TRACE</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
    <DebugType>embedded</DebugType>
    <Optimize>true</Optimize>
    <OutputPath>bin\</OutputPath>
    <DefineConstants>TRACE</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <ItemGroup>
    <Reference Include="System" />
    <Reference Include="System.Data" />
    <Reference Include="System.Drawing" />
    <Reference Include="System.Xml" />
    <Reference Include="Microsoft.CSharp" />
    <Reference Include="System.Core" />
    <Reference Include="System.Xml.Linq" />
    <Reference Include="System.Data.DataSetExtensions" />
    <Reference Include="System.Net.Http" />
    <Reference Include="System.Xaml" />
    <Reference Include="WindowsBase" />
    <Reference Include="PresentationCore" />
    <Reference Include="PresentationFramework" />
  </ItemGroup>
</Project>

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."