Roslyn，MSBuildWorkspace编译引用.NetStandard项目的.NetStandard项目会抛出“找不到RuntimeMetadataVersion值". [英] Roslyn, MSBuildWorkspace compiling a .NetStandard project referencing a .NetStandard project throws "No value for RuntimeMetadataVersion found."

问题描述

使用以下项目创建解决方案.

Create a solution with the following projects.

一个.NetStandard2.0项目，将其命名为"1"

A .NetStandard2.0 project, name it "1"

一个.NetStandard2.0项目，将其命名为"2"

A .NetStandard2.0 project, name it "2"

在2中添加项目1的引用

Add a reference of project 1 in 2

一个.Net4.6.1控制台项目将其命名为"3"，并添加nuget Microsoft.CodeAnalysis.CSharp.Workspaces v2.7.0

A .Net4.6.1 console project name it "3" and add the nuget Microsoft.CodeAnalysis.CSharp.Workspaces v2.7.0

将以下代码粘贴到项目3中

Paste in the follwing code into project 3

static void Main(string[] args)
    {
        string dir = Path.Combine(Environment.CurrentDirectory, "..\\..\\..\\");

        string solutionPath = Directory.GetFiles(dir, "*.sln").First();
        var msWorkspace = MSBuildWorkspace.Create();

        Solution solution = msWorkspace.OpenSolutionAsync(solutionPath).Result;

        DateTime date = DateTime.UtcNow;
        foreach (var project in solution.Projects.Take(2))
        {
            Compilation compilation = project.GetCompilationAsync().Result;

            using (var dllStream = new MemoryStream())
            {
                var emitResult = compilation.Emit(dllStream);
                if (emitResult.Success)
                {
                    Console.WriteLine("Success");
                }
                else
                {
                    foreach (var err in emitResult.Diagnostics)
                    {
                        Console.WriteLine($"{err.ToString()}");
                    }
                }
            }
        }
        Console.Read();
    }

执行项目3会为项目2引发以下错误，但不会为项目1引发以下错误.

executing project 3 throws the following errors for project 2, but not for project 1.

警告CS8021:未找到RuntimeMetadataVersion的值.没有找到包含System.Object的程序集，也没有通过选项指定RuntimeMetadataVersion的值.

warning CS8021: No value for RuntimeMetadataVersion found. No assembly containing System.Object was found nor was a value for RuntimeMetadataVersion specified through options.

d:\ test \ roslyntest \ 2 \ Class1.cs(1,7):错误CS0246:找不到类型或名称空间名称'System'(您是否缺少using指令或程序集引用?)

d:\test\roslyntest\2\Class1.cs(1,7): error CS0246: The type or namespace name 'System' could not be found (are you missing a using directive or an assembly reference?)

d:\ test \ roslyntest \ 2 \ Class1.cs(5,18):错误CS0518:未定义或导入'System.Object'预定义类型

d:\test\roslyntest\2\Class1.cs(5,18): error CS0518: Predefined type 'System.Object' is not defined or imported

d:\ test \ roslyntest \ 2 \ Class1.cs(5,18):错误CS1729:'对象'不包含带有0个参数的构造函数

d:\test\roslyntest\2\Class1.cs(5,18): error CS1729: 'object' does not contain a constructor that takes 0 arguments

我的问题.为什么在项目1中找不到基本类，而在项目1中找不到基类?

My question. Why is it not finding the basic classes in project 2 but in project 1?

唯一的区别是项目2引用了另一个项目.

The only difference is that project 2 references another project.

我想念什么/做错了什么?

What am i missing/doing wrong?

推荐答案

要解决此问题，您需要执行以下步骤:

To address this, here are the steps you need to take:

1. 参考 Microsoft.Build.Locator NuGet包.
2. 在创建 MSBuildWorkspace
之前，调用 MSBuildLocator.RegisterDefaults();
3. 确保您的应用程序bin文件夹中没有任何Microsoft.Build.*程序集(请参见下文).

通过这些步骤，我能够正确地构建2个项目.

With those steps I was able to correctly build the 2 projects.

这是从输出文件夹中删除文件的方法(将其添加到.csproj或使用Visual Studio中的生成后"步骤).

This is how you can remove the files from the output folder (add this to your .csproj or use the Post Build steps in Visual Studio).

  <PropertyGroup>
    <PostBuildEvent>del "$(TargetDir)\Microsoft.Build.dll"
del "$(TargetDir)\Microsoft.Build.Framework.dll"
del "$(TargetDir)\Microsoft.Build.Tasks.Core.dll"
del "$(TargetDir)\Microsoft.Build.Utilities.Core.dll"
    </PostBuildEvent>
  </PropertyGroup>

有关其他信息，请参见: https://github.com/dotnet/roslyn/issues/26029

For additional information please see: https://github.com/dotnet/roslyn/issues/26029

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