反射不适用于使用 Assembly.LoadFrom 加载的程序集 [英] Reflection not working on assembly that is loaded using Assembly.LoadFrom
问题描述
我有一个库，其中包含一些反射代码，用于检查 Asp.Net 的主要程序集、任何引用的程序集并执行很酷的操作.我试图在控制台应用程序中执行相同的确切代码，同时仍然反映 Asp.Net 的程序集，但我看到了奇怪的结果.我已经把所有的东西都连接好并且代码执行了，但是当我知道它应该返回 true 时反射代码返回 false ，因为我正在调试器中逐步执行它......这让我发疯，我不知道为什么从控制台应用程序运行时，反射表现出不同的行为.
I have a library that contains some reflection code which inspects an Asp.Net's primary assembly, any referenced assemblies and does cool stuff. I'm trying to get the same exact code to execute in a console application while still reflecting on an Asp.Net's assemblies and I'm seeing odd results. I've got everything wired up and the code executes, however the reflection code returns false when I know it should be returning true as I'm stepping through it in the debugger.. It's driving me nuts and I can't figure out why reflection is exhibiting different behavior when running from the console app.
下面是一些反射代码的完美示例，它获取 Asp.Net 应用程序中所有区域注册类型 (type.IsSubclassOf(typeof(System.Web.Mvc.AreaRegistration))).在 Asp.Net 应用程序的应用程序域中执行时，这对多种类型返回 true，但在控制台应用程序下执行时，对于这些相同类型返回 false，但仍反映那些相同的 Asp.Net 类型.
Here's a perfect example of some reflection code that gets all of the types that are area registrations in an Asp.Net application (type.IsSubclassOf(typeof(System.Web.Mvc.AreaRegistration))). This returns true for several types when executing in the app domain of an Asp.Net application, however it returns false for those same types when executed under the console application, but still reflecting on those same Asp.Net types.
我也尝试过使用 Assembly.ReflectionOnlyLoadFrom 方法，但即使在编写了所有代码来手动解析引用的程序集之后，下面显示的反射代码在应该为其返回 true 的类型上返回 false.
I've also tried using the Assembly.ReflectionOnlyLoadFrom method but even after writing all the code to manually resolve referenced assemblies the reflection code shown below returns false on types that it should be returning true for.
我可以尝试做些什么来完成这项工作?
What can I try to make this work?
public static Assembly EntryAssembly { get; set; } // this is set during runtime if within the Asp.Net domain and set manually when called from the console application.
public CodeGenerator(string entryAssemblyPath = null)
{
if (entryAssemblyPath == null) // running under the Asp.Net domain
EntryAssembly = GetWebEntryAssembly(); // get the Asp.Net main assembly
else
{
// manually load the assembly into the domain via a file path
// e:\inetpub\wwwroot\myAspNetMVCApp\bin\myApp.dll
EntryAssembly = Assembly.LoadFrom(entryAssemblyPath);
}
var areas = GetAreaRegistrations(); // returns zero results under console app domain
... code ...
}
private static List<Type> GetAreaRegistrations()
{
return EntryAssembly.GetTypes().Where(type => type.IsSubclassOf(typeof(System.Web.Mvc.AreaRegistration)) && type.IsPublic).ToList();
}
推荐答案
好的，经过大量调试后，我已经开始工作了！结果证明我的库项目是针对 Asp.Net MVC 4.0 编译的，即使 Nuget 和属性窗口声称是 5.1.Nuget/MS 再次失败.我的库所反映的 Asp.Net MVC 应用程序使用的是 MVC 5.1，因此当 Assembly.LoadFrom 和 AssemblyResolve 事件运行时，它正在加载两个版本的 System.Web.Mvc.dll 进入 LoadFrom 上下文 (4.0 & 5.1)，这导致 IsSubclassOf() 方法在预期结果时返回 false应该是真的.
Ok, after a lot of debugging I've got this working! It turned out that my library project was compiling against Asp.Net MVC 4.0 even though Nuget and the properties window claimed 5.1. Nuget/MS fail again. The Asp.Net MVC application that my library is reflecting on is using MVC 5.1 so when the Assembly.LoadFrom and the AssemblyResolve event ran it was loading two versions of System.Web.Mvc.dll into the LoadFrom context (4.0 & 5.1) and this caused the IsSubclassOf() method to return false when the expected result should have been true.
我在调试时在上面的评论中提到的非常奇怪的错误:类型System.Web.Mvc.AreaRegistration"存在于System.Web.Mvc.dll"和System.Web.Mvc"中.dll' 现在有意义，但只有在事实之后.
The very odd error I mentioned in the comments above while debugging: The type 'System.Web.Mvc.AreaRegistration' exists in both 'System.Web.Mvc.dll' and 'System.Web.Mvc.dll' now makes sense, but only after the fact.
我最终找到的方法是写出所有 AssemblyResolve 被调用来解析的程序集，并注意到 System.Web.Mvc.dll不在列表中.我启动了 程序集绑定日志查看器 并且可以清楚地看到 System.Web.Mvc.dll 被加载了两次.
The way I finally tracked this down was by writing out all of the assemblies that AssemblyResolve was called upon to resolve and noticed that System.Web.Mvc.dll was not in the list. I fired up the Assembly Binding Log Viewer and was clearly able to see that System.Web.Mvc.dll was being loaded twice.
回想起来，您应该跳过所有自定义日志记录，只使用程序集绑定日志查看器来验证每个程序集仅加载一个程序集，并且它是您期望的正确版本.
In retrospect, one should just skip all the custom logging and just use the Assembly Binding Log Viewer to verify only one of each assembly is being loaded and that it's the correct version your expecting.
弄清楚如何正确使用 AssemblyResolve 是一场噩梦，所以这里是我未完成但可用于后代的代码.
Figuring out how to use AssemblyResolve properly was a nightmare so here is my unfinished, but working code for posterity.
public class CodeGenerator
{
public static string BaseDirectory { get; set; }
public static string BinDirectory { get; set; }
static CodeGenerator()
{
BinDirectory = "bin";
// setting this in a static constructor is best practice
AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;
}
public CodeGenerator(string entryAssemblyPath = null, string baseDirectory = null, string binDirectory = null)
{
if (string.IsNullOrWhiteSpace(baseDirectory))
BaseDirectory = AppDomain.CurrentDomain.BaseDirectory;
else
BaseDirectory = baseDirectory;
if (string.IsNullOrWhiteSpace(binDirectory) == false)
BinDirectory = binDirectory;
if (entryAssemblyPath == null) // running under the Asp.Net domain
EntryAssembly = GetWebEntryAssembly(); // get the Asp.Net main assembly
else
{
// manually load the assembly into the domain via a file path
// e:\inetpub\wwwroot\myAspNetMVCApp\bin\myApp.dll
EntryAssembly = Assembly.LoadFrom(entryAssemblyPath);
}
var areas = GetAreaRegistrations(); // reflect away!
... code ...
}
static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
{
try
{
if (args == null || string.IsNullOrWhiteSpace(args.Name))
{
Logger.WriteLine("cannot determine assembly name!", Logger.LogType.Debug);
return null;
}
AssemblyName assemblyNameToLookFor = new AssemblyName(args.Name);
Logger.WriteLine("FullName is {0}", Logger.LogType.Debug, assemblyNameToLookFor.FullName);
// don't load the same assembly twice!
var domainAssemblies = AppDomain.CurrentDomain.GetAssemblies();
var skipLoading = false;
foreach (var dAssembly in domainAssemblies)
{
if (dAssembly.FullName.Equals(assemblyNameToLookFor.FullName))
{
skipLoading = true;
Logger.WriteLine("skipping {0} because its already loaded into the domain", Logger.LogType.Error, assemblyNameToLookFor.FullName);
break;
}
}
if (skipLoading == false)
{
var requestedFilePath = Path.Combine(Path.Combine(BaseDirectory, BinDirectory), assemblyNameToLookFor.Name + ".dll");
Logger.WriteLine("looking for {0}...", Logger.LogType.Warning, requestedFilePath);
if (File.Exists(requestedFilePath))
{
try
{
Assembly assembly = Assembly.LoadFrom(requestedFilePath);
if (assembly != null)
Logger.WriteLine("loaded {0} successfully!", Logger.LogType.Success, requestedFilePath);
// todo: write an else to handle load failure and search various probe paths in a loop
return assembly;
}
catch (FileNotFoundException)
{
Logger.WriteLine("failed to load {0}", Logger.LogType.Error, requestedFilePath);
}
}
else
{
try
{
// ugh, hard-coding, but I need to get on with the real programming for now
var refedAssembliesPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86), @"Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5.1");
requestedFilePath = Path.Combine(refedAssembliesPath, assemblyNameToLookFor.Name + ".dll");
Logger.WriteLine("looking for {0}...", Logger.LogType.Warning, requestedFilePath);
Assembly assembly = Assembly.LoadFrom(requestedFilePath);
if (assembly != null)
Logger.WriteLine("loaded {0} successfully!", Logger.LogType.Success, requestedFilePath);
// todo: write an else to handle load failure and search various probe paths in a loop
return assembly;
}
catch (FileNotFoundException)
{
Logger.WriteLine("failed to load {0}", Logger.LogType.Error, requestedFilePath);
}
}
}
}
catch (Exception e)
{
Logger.WriteLine("exception {0}", Logger.LogType.Error, e.Message);
}
return null;
}
}
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