使用CodeAnalysis编译C#脚本失败：缺少哪个程序集？

编译执行C#脚本时出现以下错误：

• CS0103: 名称“Queryable”在当前上下文中不存在
• CS1061: “int[]”不包含“AsQueryable”的定义，也找不到可接受第一个参数类型为“int[]”的可访问扩展方法“AsQueryable”(是否缺少using指令或程序集引用？)

已在refPaths中通过typeof(Enumerable).GetTypeInfo().Assembly.Location添加了System.Linq相关引用，但仍报错，询问缺少的程序集。

相关代码如下：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.Loader;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.Emit;

namespace CompileScript
{
    class Program
    {
        static async Task Main(string[] args)
        {
            string script = @"using System;
                              using System.Linq;

                              namespace Test { class Program {
                              public static void Main() {
                                   Console.WriteLine(""Testing a script..."");
                                   int[] arr = new int[] { 1, 2, 3};
                                   double avg = Queryable.Average(arr.AsQueryable());
                                   Console.WriteLine(""Average = "" + avg);}}}";

             var refPaths = new[] {
                   typeof(object).GetTypeInfo().Assembly.Location,
                   typeof(Console).GetTypeInfo().Assembly.Location,
                   typeof(Enumerable).GetTypeInfo().Assembly.Location,
                   Path.Combine(Path.GetDirectoryName
                   (typeof(System.Runtime.GCSettings).
                   GetTypeInfo().Assembly.Location), "System.Runtime.dll"),
             };
             SyntaxTree syntaxTree = CSharpSyntaxTree.ParseText(script);

             string assemblyName = Path.GetRandomFileName();

             MetadataReference[] references = refPaths.Select(r => MetadataReference.
             CreateFromFile(r)).ToArray();

             CSharpCompilation compilation = CSharpCompilation.Create(
                  assemblyName,
                  syntaxTrees: new[] { syntaxTree },
                  references: references,
                  options: new CSharpCompilationOptions
                  (OutputKind.DynamicallyLinkedLibrary));

            using var ms = new MemoryStream();
            EmitResult result = compilation.Emit(ms);

            if (!result.Success)
            {
                   IEnumerable<Diagnostic> failures =
                        result.Diagnostics.Where(diagnostic =>
                        diagnostic.IsWarningAsError ||
                        diagnostic.Severity == DiagnosticSeverity.Error);

                   foreach (Diagnostic diagnostic in failures)
                   {
                      Console.WriteLine("\t{0}: {1}", diagnostic.Id,
                                                      diagnostic.GetMessage());
                   }
             }
             else
             {
                  ms.Seek(0, SeekOrigin.Begin);

                  Assembly assembly = AssemblyLoadContext.Default.LoadFromStream(ms);
                  var type = assembly.GetType("Test.Program");
                  var instance = assembly.CreateInstance("Test.Program");
                  MethodInfo? methodInfo = type.GetMethod("Main");
                  methodInfo.Invoke(instance, null);
              }
          }
       }
   }

你缺少的是包含System.Linq.Queryable类型的程序集引用。Queryable类以及AsQueryable扩展方法均定义在该程序集中——虽然Enumerable和Queryable同属System.Linq命名空间，但在部分.NET版本中二者分属不同程序集，即便在.NET Core/.NET 5+环境下，也需显式引用包含Queryable的程序集。

只需在refPaths数组中添加以下条目即可解决：

typeof(System.Linq.Queryable).GetTypeInfo().Assembly.Location

修改后的refPaths示例：

var refPaths = new[] {
    typeof(object).GetTypeInfo().Assembly.Location,
    typeof(Console).GetTypeInfo().Assembly.Location,
    typeof(Enumerable).GetTypeInfo().Assembly.Location,
    typeof(System.Linq.Queryable).GetTypeInfo().Assembly.Location, // 新增引用Queryable所在程序集
    Path.Combine(Path.GetDirectoryName
    (typeof(System.Runtime.GCSettings).
    GetTypeInfo().Assembly.Location), "System.Runtime.dll"),
};

内容的提问来源于stack exchange，提问作者lucidgold