Visual Studio 2026构建报错：'<‘是无效值起始符及关联问题咨询

阿华AIGC实验室

2026-6-1

问题：Visual Studio 2026构建报错“'<‘是无效值起始符”，关联Microsoft.WebTools.Aspire.targets及Azure.Identity包

使用Visual Studio 2026（最新社区版）构建项目时，出现错误：'<‘是无效值起始符。行号：2 | 字节位置：0，指向文件C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Microsoft\VisualStudio\WebTools.Aspire\Microsoft.WebTools.Aspire.targets
项目可正常运行，但涉事项目的编辑器存在异常：鼠标悬停在IEnumerable上时无语法高亮和描述弹窗
重装Windows 11后问题消失一周，现已复现；团队3名开发者中仅本人遇到该问题
项目未引用Aspire，也无自定义构建流程
排查发现：错误提示返回的XML经验证合法，是某程序将该XML文件当作JSON解析；且使用Azure.Identity NuGet包1.20.0及更高版本时会触发此错误

报错高亮的XML代码段：

<GenerateCombinedAppSettingsSchema
  AppSettingJsonSchemaFilePath="$(AppSettingJsonSchemaLoadFilePath)"
  ComponentJsonSchemaCombinedFilePath="$(JsonSchemaCombinedFilePath)"
  AppSettingsJsonSchemaCombinedFilePath="$(AppSettingsJsonSchemaCombinedFilePath)">
</GenerateCombinedAppSettingsSchema>

完整的Microsoft.WebTools.Aspire.targets文件内容：

<?xml version="1.0" encoding="utf-8"?>

<!--
***********************************************************************************************
Microsoft.WebTools.Aspire.targets

WARNING:  DO NOT MODIFY this file unless you are knowledgeable about MSBuild and have
          created a backup copy.  Incorrect changes to this file will make it
          impossible to load or build your projects from the command-line or the IDE.

Copyright (C) Microsoft Corporation. All rights reserved.
***********************************************************************************************
-->

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <UsingTask
      TaskName="Microsoft.WebTools.Aspire.MSBuild.GenerateCombinedComponentSchema"
      AssemblyFile="Microsoft.WebTools.Aspire.MSBuild.dll" />
  <UsingTask
      TaskName="Microsoft.WebTools.Aspire.MSBuild.GenerateCombinedAppSettingsSchema"
      AssemblyFile="Microsoft.WebTools.Aspire.MSBuild.dll" />

  <PropertyGroup>
    <JsonSchemaCombinedFilePath>$(IntermediateOutputPath)\CombinedComponentSchema.json</JsonSchemaCombinedFilePath>
    <JsonSchemaCombinedFilePath>$([MSBuild]::NormalizePath($(MSBuildProjectDirectory), $(JsonSchemaCombinedFilePath)))</JsonSchemaCombinedFilePath>
    <AppSettingsJsonSchemaCombinedFilePath>$(IntermediateOutputPath)\AppSettingsSchema.json</AppSettingsJsonSchemaCombinedFilePath>
    <AppSettingsJsonSchemaCombinedFilePath>$([MSBuild]::NormalizePath($(MSBuildProjectDirectory), $(AppSettingsJsonSchemaCombinedFilePath)))</AppSettingsJsonSchemaCombinedFilePath>
    <SchemaGenIncrementalBuildInputs>@(JsonSchemaSegment);$(ProjectAssetsFile)</SchemaGenIncrementalBuildInputs>
  </PropertyGroup>

  <Target Name="GenerateCombinedComponentSchemaTarget"
          Condition=" '@(JsonSchemaSegment)' != '' "
          Inputs="$(SchemaGenIncrementalBuildInputs)"
          Outputs="$(JsonSchemaCombinedFilePath)">
    <GenerateCombinedComponentSchema
      JsonSchemaSegmentFiles="@(JsonSchemaSegment)"
      JsonSchemaCombinedFilePath="$(JsonSchemaCombinedFilePath)">
    </GenerateCombinedComponentSchema>
  </Target>

  <Target Name="GenerateCombinedAppSettingsSchemaTarget"
          DependsOnTargets="GenerateCombinedComponentSchemaTarget"
          Condition=" '@(JsonSchemaSegment)' != '' "
          BeforeTargets="CompileDesignTime"
          Inputs="$(SchemaGenIncrementalBuildInputs);$(JsonSchemaCombinedFilePath)"
          Outputs="$(AppSettingsJsonSchemaCombinedFilePath)">
    <GenerateCombinedAppSettingsSchema
      AppSettingJsonSchemaFilePath="$(AppSettingJsonSchemaLoadFilePath)"
      ComponentJsonSchemaCombinedFilePath="$(JsonSchemaCombinedFilePath)"
      AppSettingsJsonSchemaCombinedFilePath="$(AppSettingsJsonSchemaCombinedFilePath)">
    </GenerateCombinedAppSettingsSchema>
    <Message Text="Generating appsettingsschema" />
  </Target>
  
  <Target Name="CleanupCombinedAppSettingsSchemaTarget"
          Condition=" '@(JsonSchemaSegment)' == '' "
          BeforeTargets="CompileDesignTime">
    <Delete Files="$(AppSettingsJsonSchemaCombinedFilePath)" />
    <Message Text="Deleting appsettingsschema" />
  </Target>
</Project>

解决方案

1. 禁用Aspire相关MSBuild目标

由于项目未引用Aspire，可手动在项目文件（.csproj）中添加配置，阻止加载Aspire的targets文件：

<PropertyGroup>
  <DisableAspireSchemaGeneration>true</DisableAspireSchemaGeneration>
</PropertyGroup>

或者直接排除该targets文件的导入：

<ItemGroup>
  <MSBuildRemoveTargets Include="Microsoft.WebTools.Aspire.targets" />
</ItemGroup>

2. 回退Azure.Identity包版本

暂时将Azure.Identity回退到1.19.0版本，确认是否解决问题：

Install-Package Azure.Identity -Version 1.19.0

后续关注Azure.Identity官方更新，看是否修复了触发Aspire目标的问题。

3. 重置Visual Studio组件缓存

关闭Visual Studio
删除以下目录的缓存文件：
- %LOCALAPPDATA%\Microsoft\VisualStudio\18.0_*\ComponentModelCache
- %USERPROFILE%\.nuget\packages\azure.identity（删除对应版本后重新安装）
重新打开Visual Studio并清理重建项目