c# - Roslyn - 从内存中程序集创建元数据引用

Question

使用 ASP.NET 5 应用程序 (Visual Studio 2015 CTP5) 和 Microsoft.CodeAnalysis.CSharp。

如果我尝试为作为解决方案一部分的程序集创建 MetadataReference，以将其作为对 CSharpCompilation.Create 的引用传递，我会收到 System.ArgumentException，“空路径名不合法”。

// Throws exception
MetadataReference.CreateFromAssembly(typeof(this).Assembly);

// Doesn't throw exception
MetadataReference.CreateFromAssembly(typeof(Object).Assembly);

如果我检查程序集的 Location 属性，它是空的。我假设这与在 ASP.NET 5 中在内存中编译应用程序的新方法有关，因此程序集不会存储在光盘上。

那么有没有办法为没有 Location 属性的程序集传递对 Roslyn 的引用，或者这目前不受支持？

编辑:@JaredPar - @SLaks 已经突出显示了它失败的确切位置，但这里是完整的堆栈跟踪信息。在此之前，我正在从 System.* 程序集创建其他几个 MetadataReferences，其中任何一个都没有问题。

System.ArgumentException
Empty path name is not legal.
C:\Development\Incubator\net.framework\src\Webfuel.Services.Host\ScriptHelper\ScriptHelper.cs
Line 86:  
Line 87:              // Compile the code
Line 88:              var compilation = CSharpCompilation.Create(
Line 89:                  assemblyName,
Line 90:                  options: new CSharpCompilationOptions(outputKind: OutputKind.DynamicallyLinkedLibrary),
 at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, Win32Native.SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share) 
at System.IO.File.OpenRead(String path) 
at Microsoft.CodeAnalysis.InternalUtilities.FileStreamLightUp.OpenFileStream(String path) 
at Microsoft.CodeAnalysis.MetadataReference.CreateFromAssembly(Assembly assembly, MetadataReferenceProperties properties, DocumentationProvider documentation) 
at Microsoft.CodeAnalysis.MetadataReference.CreateFromAssembly(Assembly assembly) 
at Webfuel.Services.Host.ScriptHelper.CompileScriptImpl(String source) in C:\Development\Incubator\net.framework\src\Webfuel.Services.Host\ScriptHelper\ScriptHelper.cs:line 88 
at Webfuel.Services.Host.ScriptHelper.<>c__DisplayClass0.<CompileTemplate>b__3(String source) in C:\Development\Incubator\net.framework\src\Webfuel.Services.Host\ScriptHelper\ScriptHelper.cs:line 71 
at System.Collections.Concurrent.ConcurrentDictionary<TKey, TValue>.GetOrAdd(TKey key, Func<TKey, TValue> valueFactory) 
at Webfuel.Services.Host.ScriptHelper.CompileTemplate(String template) in C:\Development\Incubator\net.framework\src\Webfuel.Services.Host\ScriptHelper\ScriptHelper.cs:line 69 
at Webfuel.Services.Host.SandboxContext.<ExecuteTemplateAsync>d__1.MoveNext() in C:\Development\Incubator\net.framework\src\Webfuel.Services.Host\SandboxContext.cs:line 176 
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter<TResult>.GetResult() 
at Webfuel.Services.Host.SandboxHost.<ExecuteTemplateAsync>d__1.MoveNext() in C:\Development\Incubator\net.framework\src\Webfuel.Services.Host\SandboxHost.cs:line 39 
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter<TResult>.GetResult() 
at Webfuel.Services.Sandbox.SandboxService.<ExecuteTemplateAsync>d__1.MoveNext() in C:\Development\Incubator\net.framework\src\Webfuel.Services.Sandbox\SandboxService.cs:line 47 
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter<TResult>.GetResult() 
at Webfuel.Services.Server.ServerService.<ProcessContentRequestAsync>d__1.MoveNext() in C:\Development\Incubator\net.framework\src\Webfuel.Services.Server\ServerService.cs:line 179 
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter<TResult>.GetResult() 
at Webfuel.Services.Server.ServerService.<ProcessRequestAsync>d__1.MoveNext() in C:\Development\Incubator\net.framework\src\Webfuel.Services.Server\ServerService.cs:line 73 
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter<TResult>.GetResult() 
at Webfuel.App.ServerMiddleware.<Invoke>d__1.MoveNext() in C:\Development\Incubator\net.framework\src\Webfuel.App\Startup.cs:line 89 
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.GetResult() 
at Microsoft.AspNet.RequestContainer.ContainerMiddleware.<Invoke>d__1.MoveNext() 
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.GetResult() 
at Microsoft.AspNet.Loader.IIS.KlrHttpApplication.<ProcessRequestAsyncImpl>d__1.MoveNext() 
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.GetResult() 
at Microsoft.AspNet.Loader.IIS.HttpApplicationBase.<InvokeProcessRequestAsyncImpl>d__1.MoveNext()

Answer 1

已经有一段时间了，但我确实在 github Roslyn 存储库上得到了答案，所以我会发布它以防有人发现这个问题:

ASP.NET 5 为此提供了一个 API。你可以做 Razor 做的事 https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNet.Mvc.Razor/Compilation/RoslynCompilationService.cs#L132

这回到了 Asp.Net 5 的 Beta1 左右，因此可能需要调整，但原理仍然相同 - 遵循 Asp.Net 本身通过服务注入(inject)器将使用的 IAssemblyLoadContextAccessor 使用的 API提供。

感谢大卫·福勒

更新:此答案适用于 ASP.NET 5 Beta1。 API 发生了很大变化，在 Core 1.0 中，您可以从静态成员访问 AssemblyLoadContext 而不是使用 IAssemblyLoadContextAccessor:

System.Runtime.Loader.AssemblyLoadContext.Default

然后您可以调用 LoadFromStream 从二进制图像加载程序集。这是我使用的代码的粗略草图，删除了一些不相关的位:

        // Give the assembly a unique name
        var assemblyName = "Gen" + Guid.NewGuid().ToString().Replace("-", "") + ".dll";

        // Build the syntax tree
        var syntaxTree = CSharpSyntaxTree.ParseText(source);

        // Compile the code
        var compilation = CSharpCompilation.Create(
            assemblyName,
            options: new CSharpCompilationOptions(outputKind: OutputKind.DynamicallyLinkedLibrary),
            syntaxTrees: new List<SyntaxTree> { syntaxTree },
            references: GetMetadataReferences());

        // Emit the image of this assembly 
        byte[] image = null;
        using (var ms = new MemoryStream())
        {
            var emitResult = compilation.Emit(ms);
            if (!emitResult.Success)
            {
                throw new InvalidOperationException();
            }
            image = ms.ToArray();
        }

        Assembly assembly = null;

        // NETCORE
        using (var stream = new MemoryStream(image))
            assembly = System.Runtime.Loader.AssemblyLoadContext.Default.LoadFromStream(stream);

这不应该按原样运行，而只是给出主要步骤的概念。

此外，从仅内存中的程序集生成元数据引用的问题也不再存在，因为这些在 Core 1.0 中不再存在，因此每个程序集都有一个 Location 属性。所以获取这些引用基本上与 ASP.net 4 中的过程相同:

MetadataReference.CreateFromFile(Assembly.Load(new AssemblyName(assemblyName)).Location);