Roslyn Workspace API加载第三方解决方案无法获取Document实例

我尝试使用Roslyn Workspace API枚举第三方解决方案中每个Project实例下的所有Document项，编写的代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.MSBuild;


string slnPath = "ThirdPartySolution.sln";

MSBuildWorkspace workspace = MSBuildWorkspace.Create();
Solution s = await workspace.OpenSolutionAsync("ThirdPartySolution.sln");

foreach (Project p in s.Projects)
{
    Console.WriteLine(p.Name);
    Console.WriteLine(p.Documents.Count());
        
    foreach (Document d in p.Documents)
    {
        Console.WriteLine("\t" + d.Name);
    }
}

workspace.Dispose();

该代码基于.NET Core构建运行无错误，能正常打印解决方案中的项目名称，但每个Project对象的Document实例计数始终为0。

为排查问题，添加了诊断代码：

foreach (WorkspaceDiagnostic diagnostic in workspace.Diagnostics)
{
    Console.WriteLine(diagnostic.Message);
}

得到的诊断信息如下：

找不到导入的项目"C:\Program Files\Microsoft Visual Studio\2022\Professional\MSBuild\Current\Bin\amd64\Current\Microsoft.Common.props"。确认导入声明中的表达式正确，且文件存在于磁盘上。
C:\Program Files\dotnet\sdk\6.0.408\Sdks\Microsoft.NET.Sdk\Sdk\Sdk.props

经检查，上述不存在的路径确实未找到，另一路径存在。但该解决方案在Visual Studio 2022中通过菜单构建和命令行msbuild构建均正常，请问问题出在哪里？

问题原因 #

出现此问题的核心原因是：Roslyn的MSBuildWorkspace默认会使用NuGet包中附带的MSBuild版本，而非本地Visual Studio安装的MSBuild环境，这导致项目文件在解析时出现路径错误，无法正确加载项目关联的文档资源。

修正方案 #

1. 完整可运行代码 #

需要引入Microsoft.Build.Locator并注册默认MSBuild实例，修改后的代码如下：

// Program.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.MSBuild;
using Microsoft.Build.Locator;

string slnPath = "ThirdPartySolution.sln";

// 注册本地安装的MSBuild实例
MSBuildLocator.RegisterDefaults();

MSBuildWorkspace workspace = MSBuildWorkspace.Create();
Solution s = await workspace.OpenSolutionAsync(slnPath);

// 输出诊断信息验证修复效果
foreach (WorkspaceDiagnostic diagnostic in workspace.Diagnostics)
{
    Console.WriteLine(diagnostic.Message);
}

foreach (Project p in s.Projects)
{
    Console.WriteLine(p.Name);
    Console.WriteLine(p.Documents.Count());
        
    foreach (Document d in p.Documents)
    {
        Console.WriteLine("\t" + d.Name);
    }
}

workspace.Dispose();

2. 项目包引用配置 #

需确保项目文件中，除Microsoft.Build.Locator外，所有Microsoft.Build.*系列包引用都设置ExcludeAssets="runtime"，避免与本地MSBuild环境冲突：

<ItemGroup>
    <PackageReference Include="Microsoft.Build" Version="17.7.2"
        ExcludeAssets="runtime"/>
    <PackageReference Include="Microsoft.Build.Framework" Version="17.7.2"
        ExcludeAssets="runtime"/>
    <PackageReference Include="Microsoft.Build.Locator" Version="1.6.10" />
    <PackageReference Include="Microsoft.Build.Utilities.Core" Version="17.7.2"
        ExcludeAssets="runtime"/>
    <PackageReference Include="Microsoft.CodeAnalysis" Version="4.7.0" />
    <PackageReference Include="Microsoft.CodeAnalysis.Workspaces.MSBuild" Version="4.7.0" />
  </ItemGroup>

内容的提问来源于stack exchange，提问作者user32882