【发布时间】：2011-04-02 06:30:49
【问题描述】：
我有一个名为 EcmaEval 的类，它允许我的应用程序的用户执行任意 javascript。类的实现在这个问题的最后。我允许用户访问一个“环境”对象，该对象提供对他们编写脚本有用的方法和属性。
问题是我需要向 JScript 公开一个 C# 动态对象，但它不起作用。有没有人这样做过 - 它应该工作吗？
所以，如果我有一个普通的旧对象，它带有一个名为 name 的字符串属性，它就可以工作：
test test = new test();
test.Name = "Daniel Bryars";
EcmaEval ecmaEval = new EcmaEval(new List<String>
{
Assembly.GetExecutingAssembly().Location
}, test);
String ecma = "environment.Name";
String result = ecmaEval.Eval<String>(ecma);
Assert.AreEqual("Daniel Bryars", result);
但是如果我将我的 EcmaEval 对象传递给一个动态对象，那么它不会（属性名称为空）：
dynamic expandoObject = new ExpandoObject();
expandoObject.Name = "Daniel Bryars";
EcmaEval ecmaEval = new EcmaEval(new List<String>
{
Assembly.GetExecutingAssembly().Location
}, expandoObject);
String ecma = "environment.Name";
String result = ecmaEval.Eval<String>(ecma);
Assert.AreEqual("Daniel Bryars", result);
（结果为空。）
这里是 EcmaEval 的实现。涉及另一个名为 JSObjectToDotNetConversion 的类，它将 JSObject 强制转换为 C# 对象（它使用反射来新建 C# 对象并设置字段和/或属性），但该类的实现无关紧要。
using System;
using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Reflection;
using Microsoft.JScript;
namespace Aeriandi.ApplicationBlocks.BusinessBaseObjects.Ecma
{
/// <summary>
/// Exposes the JScrip eval function as a .net method.
/// This uses the "safe" JScript.Eval so no disk, or network access is allowed.
/// </summary>
public class EcmaEval
{
private readonly object _evaluator;
private readonly Type _evaluatorType;
private readonly Object _environment;
public EcmaEval() : this (new List<string>(), null )
{
}
public EcmaEval(List<String> referencedAssemblies, Object environment)
{
if (null == referencedAssemblies)
{
throw new ArgumentNullException("referencedAssemblies", "The argument referencedAssemblies must not be null");
}
_environment = environment;
JScriptCodeProvider compiler = new JScriptCodeProvider();
CompilerParameters parameters = new CompilerParameters();
parameters.GenerateInMemory = true;
foreach (String referencedAssembly in referencedAssemblies)
{
parameters.ReferencedAssemblies.Add(referencedAssembly);
}
string _jscriptSource =
@"package Evaluator
{
class Evaluator
{
public function Eval(expr : String, environment : Object)
{
return eval(expr);
}
}
}";
CompilerResults results = compiler.CompileAssemblyFromSource(parameters, _jscriptSource);
Assembly assembly = results.CompiledAssembly;
_evaluatorType = assembly.GetType("Evaluator.Evaluator");
_evaluator = Activator.CreateInstance(_evaluatorType);
}
public Object Eval(Type returnType, String ecmaScript)
{
ecmaScript = WrapInBrackets(ecmaScript);
Object result = _evaluatorType.InvokeMember(
"Eval",
BindingFlags.InvokeMethod,
null,
_evaluator,
new object[] { ecmaScript, _environment }
);
return JSObjectToDotNetConversion.Coerce(returnType, result);
}
public T Eval<T>(String ecmaScript)
{
return (T) Eval(typeof (T), ecmaScript);
}
private static String WrapInBrackets(String ecmaScript)
{
//You can't start a block of js with a { because it's ambiguous (according to the spec)
//so we wrap everything in brackets.
return String.Format("({0})", ecmaScript);
}
}
}
【问题讨论】：
标签： dynamic c#-4.0 javascript