新应用程序域加载动态代码生成的程序集失败 提示找不到指定文件

我有一个asp.net应用，可从用户脚本动态生成程序集，原有功能运行正常。现在我想要在低权限的SandBox应用程序域中运行生成的程序集，但在新应用程序域加载程序集时抛出以下异常：

Could not load file or assembly 'genb3336c1d82074079911fb70bd8bd7e65.dll, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.

为了排查问题，我把生成的程序集保存到磁盘，编写了简单测试程序，代码如下：

string path = @"test.dll";
byte[] buffer = File.ReadAllBytes(path);

var assembly = AppDomain.CurrentDomain.Load(buffer); //此行执行正常

var appDomain = AppDomain.CreateDomain("Test");
assembly = appDomain.Load(buffer); //此行抛出异常

测试结果还是在新域加载程序集时报相同错误，在当前域加载则完全正常。
随后我用生成该dll的源码手动创建了一个类库项目，源码非常精简，方法内仅2行代码，编译得到的dll在新应用程序域中可正常加载。
我用ILSpy打开两个dll对比，结构完全一致：

我现在完全找不到生成的dll的问题所在，我使用如下代码生成程序集：

public class ScriptCompiler
{
    public static (byte[], byte[], Assembly) Compile((string Source, string Path)[] sources, string[] references, params Type[] types)
    {
        var assemblyName = "gen" + Guid.NewGuid().ToString().Replace("-", "") + ".dll";
        byte[] rawAssembly;
        byte[] rawPdb;

#if DEBUG
        var encoding = Encoding.UTF8;
        var symbolsName = Path.ChangeExtension(assemblyName, "pdb");

        var sourceTexts = sources
            .Select(s => new { Buffer = encoding.GetBytes(s.Source), s.Source, s.Path })
            .Select(b => new { SourceText = SourceText.From(b.Buffer, b.Buffer.Length, encoding, canBeEmbedded: true), b.Path });

        var syntaxTrees = sourceTexts
            .Select(s => new { Tree = CSharpSyntaxTree.ParseText(s.SourceText, new CSharpParseOptions(), s.Path), s.Path })
            .Select(t => new { Node = t.Tree.GetRoot() as CSharpSyntaxNode, t.Path })
            .Select(n => CSharpSyntaxTree.Create(n.Node, null, n.Path, encoding));

        var options = new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary).WithOptimizationLevel(OptimizationLevel.Debug);
#else
        var syntaxTrees = 
            from source in sources.Select(s => s.Source)
            select CSharpSyntaxTree.ParseText(source);

        var options = new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary).WithOptimizationLevel(OptimizationLevel.Release);
#endif

        var typeRefs = new List<MetadataReference>();
        foreach (var type in types)
        {
            typeRefs.Add(MetadataReference.CreateFromFile(type.Assembly.Location));
        }

        var compilation = CSharpCompilation.Create(assemblyName,
            options: options,
            syntaxTrees: syntaxTrees,
            references: typeRefs.Union(references.Select(r => MetadataReference.CreateFromFile(r))));

        EmitResult emitResult;

        using (var peStream = new MemoryStream())
        using (var pdbStream = new MemoryStream())
        {
#if DEBUG
            emitResult = compilation.Emit(
                peStream: peStream,
                pdbStream: pdbStream,
                embeddedTexts: sourceTexts.Select(s => EmbeddedText.FromSource(s.Path, s.SourceText)),
                options: new EmitOptions(debugInformationFormat: DebugInformationFormat.PortablePdb, pdbFilePath: symbolsName)
            );
#else
            emitResult = compilation.Emit(peStream: peStream);
#endif

            if (emitResult.Success)
            {
                rawAssembly = peStream.GetBuffer();
                rawPdb = pdbStream.GetBuffer();
                var assembly = Assembly.Load(rawAssembly, rawPdb);
                return (rawAssembly, rawPdb, assembly);
            }
        }

        var message = string.Join("\r\n", emitResult.Diagnostics);
        throw new ApplicationException(message);
    }
}

请问是什么原因导致的吗？
补充：
以下是fusionLog日志，我不清楚该怎么解读它：

=== Pre-bind state information ===
LOG: DisplayName = genb3336c1d82074079911fb70bd8bd7e65.dll, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null
 (Fully-specified)
LOG: Appbase = file:///C:/Users/Admin/source/repos/LoadAssembly/LoadAssembly/bin/Debug/
LOG: Initial PrivatePath = NULL
Calling assembly : (Unknown).
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Users\Admin\source\repos\LoadAssembly\LoadAssembly\bin\Debug\LoadAssembly.exe.Config
LOG: Using host configuration file: 
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\v4.0.30319\config\machine.config.
LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind).
LOG: Attempting download of new URL file:///C:/Users/Admin/source/repos/LoadAssembly/LoadAssembly/bin/Debug/genb3336c1d82074079911fb70bd8bd7e65.dll.DLL.
LOG: Attempting download of new URL file:///C:/Users/Admin/source/repos/LoadAssembly/LoadAssembly/bin/Debug/genb3336c1d82074079911fb70bd8bd7e65.dll/genb3336c1d82074079911fb70bd8bd7e65.dll.DLL.
LOG: Attempting download of new URL file:///C:/Users/Admin/source/repos/LoadAssembly/LoadAssembly/bin/Debug/genb3336c1d82074079911fb70bd8bd7e65.dll.EXE.
LOG: Attempting download of new URL file:///C:/Users/Admin/source/repos/LoadAssembly/LoadAssembly/bin/Debug/genb3336c1d82074079911fb70bd8bd7e65.dll/genb3336c1d82074079911fb70bd8bd7e65.dll.EXE.

问题原因 #

从fusion日志可以直接定位核心问题：你调用CSharpCompilation.Create时，把带.dll后缀的文件名直接当成了程序集名称传入，导致程序集的内置名称自带.dll后缀。新AppDomain加载程序集时会把这个后缀当成名称的一部分，去磁盘探测xxx.dll.dll文件，自然找不到对应资源。
而AppDomain.CurrentDomain.Load(byte[])走的是直接加载原始字节流的逻辑，不会触发磁盘文件探测，所以当前域加载完全正常。你手动编译的类库项目默认程序集名称不带后缀，所以可以正常加载。

修复方案 #

修改编译代码中程序集名称的生成逻辑，去掉.dll后缀即可：

// 原错误代码
var assemblyName = "gen" + Guid.NewGuid().ToString().Replace("-", "") + ".dll";
// 修正为
var assemblyName = "gen" + Guid.NewGuid().ToString().Replace("-", "");

如果需要指定输出dll的文件名，在编译完成后保存到磁盘时再加后缀即可，不要把后缀写到程序集的内置名称里。

优化建议 #

如果是沙盒AppDomain场景，更推荐用代理类的方式加载内存程序集，避免跨域传递Assembly对象带来的权限泄漏风险：

1. 先定义一个继承MarshalByRefObject的跨域代理类
2. 在新AppDomain中实例化代理类
3. 在代理类内部执行Assembly.Load(byte[])加载程序集、执行业务逻辑
   这种方式完全基于内存加载，不需要依赖磁盘文件，更符合沙盒场景的安全需求。

内容的提问来源于stack exchange，提问作者alfoks