中等信任度的匿名类型，与反射一起使用，而不是与表达式一起使用

发布于 2024-11-30 05:36:04 字数 957 浏览 5 评论 0原文

我在 Medium Trust 中对 Linq 查询进行自定义投影，并收到 MethodAccessException 或 TypeAccessException 抱怨反射和安全权限。

我已将代码简化为以下内容：

var anon1 = new { Name = "Bill Gates" };
var ctor = anon1.GetType().GetConstructors().First();

// With native Reflection it works
var anon2 = ctor.Invoke(new object[] { "Steve Ballmer" });

var expr = Expression.New(ctor, Expression.Constant("Scott Guthrie"));
var lamb = Expression.Lambda(expr);      // This throws in Medium Trust

var anon3 = lamb.Compile().DynamicInvoke();

anon1.ToString();        // --> { Name = Bill Gates }
anon2.ToString();        // --> { Name = Steve Ballmer }
anon3.ToString();        // --> { Name = Scott Guthrie }

在完全信任中，将创建 anon2 和 anon3。在中等信任中，只会创建 anon2。

另一个类似情况没有解决问题

原文

I'm doing custom projections on Linq queries in Medium Trust and I get a MethodAccessException or TypeAccessException complaining about reflection and security rights.

I've simplified the code to the following:

var anon1 = new { Name = "Bill Gates" };
var ctor = anon1.GetType().GetConstructors().First();

// With native Reflection it works
var anon2 = ctor.Invoke(new object[] { "Steve Ballmer" });

var expr = Expression.New(ctor, Expression.Constant("Scott Guthrie"));
var lamb = Expression.Lambda(expr);      // This throws in Medium Trust

var anon3 = lamb.Compile().DynamicInvoke();

anon1.ToString();        // --> { Name = Bill Gates }
anon2.ToString();        // --> { Name = Steve Ballmer }
anon3.ToString();        // --> { Name = Scott Guthrie }

In Full Trust, anon2 and anon3 will be created. In Medium Trust only anon2 will be created.

Another similar situation did not solve the issue

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飘然心甜 2024-12-07 05:36:04

这是因为编译器将匿名类型创建为内部。这意味着程序集外部的代码将无法访问这些类型。当您自己进行反射时，所有调用都来自您的程序集，因此这是允许的。但是，当您引入表达式时，调用开始来自框架 DLL，因此它们会停止。

解决此类问题的一种简单方法是使用 InternalsVisibleTo 属性。只需添加以下内容即可：

[assembly: InternalsVisibleTo("System.Core")]

您将能够创建 lambda。然而，当你去编译它时，你会得到类似的权限异常。在这种情况下，Compile 方法最终会触发 mscorlib.dll 中的一些代码来尝试访问您的类型。我尝试添加：

[assembly: InternalsVisibleTo("mscorlib")]

但这似乎不起作用。我认为这可能与 mscorlib 是强签名的事实有关。根据InternalsVisislbeTo的文档：

当前程序集和友元程序集都必须未签名，或者
两者都必须使用强名称进行签名。

也许如果您的代码已签名，它就会起作用。或者也许您甚至不需要调用 Compile() - 也许这只是为了测试？添加对 System.Core 的引用值得一试。

This is caused because anonymous types are created as internal by the compiler. That means code outside of your assembly won't be able to access the types. When you do the reflection yourself, all the calls are coming from your assembly so it is allowed. But when you introduce expressions, the calls start coming from framework DLLs and so they get stopped.

An easy way to solve problems of this nature is with the InternalsVisibleTo attribute. By just adding this:

[assembly: InternalsVisibleTo("System.Core")]

you'll be able to create the lambda. However, when you go to compile it, you get a similar permission exception. In that case, the Compile method ends up triggering some code in mscorlib.dll to try to access your type. I tried adding:

[assembly: InternalsVisibleTo("mscorlib")]

but that didn't seem to work. I think it might have to do with the fact that mscorlib is strongly signed. According to the documentation of InternalsVisislbeTo:

Both the current assembly and the friend assembly must be unsigned, or
both must be signed with a strong name.

Perhaps if your code was signed, it would work. Or perhaps you don't even need the call to Compile() - maybe that was just for testing? Adding the reference to System.Core is worth a try.

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