Roslyn - 编译简单类:“找不到类型或命名空间名称 'string'..."

我正在使用 Roslyn API 来生成和编译一个类.生成的类如下所示:

I'm using the Roslyn API to generate and compile a class. The generated class looks like this:

namespace MyCompany.Product
{
    public class TestClass
    {
        public void Configure(string id)
        {
        }
    }
}

然而，当我编译它时，Emit(ted) 结果给出:

However, when i come to compile it, the Emit(ted) result gives:

错误 CS0246:找不到类型或命名空间名称字符串"(您是否缺少 using 指令或程序集引用?)

error CS0246: The type or namespace name 'string' could not be found (are you missing a using directive or an assembly reference?)

这是执行编译的方法:

    private static readonly IEnumerable<string> DefaultNamespaces = new[]
        {
            "System",
            "System.IO",
            "System.Net",
            "System.Linq",
            "System.Text",
            "System.Text.RegularExpressions",
            "System.Collections.Generic"
        };

    public void Compile(IEnumerable<SyntaxTree> syntaxes, string targetPath)
    {

        var assemblyPath = Path.GetDirectoryName(typeof(object).Assembly.Location);
        // assemblyPath = "C:\Windows\Microsoft.NET\Framework64\v4.0.30319"

        IEnumerable<MetadataReference> defaultReferences = new[]
        {
            MetadataReference.CreateFromFile(Path.Combine(assemblyPath, "mscorlib.dll")),
            MetadataReference.CreateFromFile(Path.Combine(assemblyPath, "System.dll")),
            MetadataReference.CreateFromFile(Path.Combine(assemblyPath, "System.Core.dll")),
            MetadataReference.CreateFromFile(Path.Combine(assemblyPath, "System.Runtime.dll")),

        };
        CSharpCompilationOptions defaultCompilationOptions = new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
                    .WithOverflowChecks(true).WithOptimizationLevel(OptimizationLevel.Release)
                    .WithUsings(DefaultNamespaces);

        CSharpCompilation compilation = CSharpCompilation.Create(
            targetPath,
            syntaxTrees: syntaxes,
            references: defaultReferences,
            options: defaultCompilationOptions);

        using (var ms = new MemoryStream())
        {
            EmitResult result = compilation.Emit(ms);
            // here, result.Success = false, with it's Diagnostics collection containing the error
            if (!result.Success)
            {
            } 
        }
    }

但是，如果我编译下面的类，但使用类型为string"的常量，它会按预期编译，因此当声明为方法参数类型时，它不喜欢string":

However, if I compile the below class, but using a constant of type 'string', it compiles as expected, so it doesn't like 'string' when declared as a method parameter type:

namespace MyCompany.Product
{
    public class TestClass
    {
        public const string Id = "e1a64bdc-936d-47d9-aa10-e8634cdd7070";
    }
}

我使用的是框架 4.6.1，Microsoft.CodeAnalysis 版本=1.3.1.0

I'm using framework 4.6.1, Microsoft.CodeAnalysis Version=1.3.1.0