c# - 反射方法AccessException

Question

我在 Silverlight 中有一个简单的代码:

public void temp()
{
    try
    {                
        WriteableBitmap obj = new WriteableBitmap(10, 10);

        //PropertyInfo pr = obb.GetType().GetProperty("Pixels");
        Type type = obj.GetType();
        Type typeofType = type.GetType();

        MethodInfo getPropMethod = typeofType.GetMethod("GetProperty", new Type[] { typeof(string) }); //get method info
        PropertyInfo pix1 = type.GetProperty("Pixels"); // first call - no exceptions
        PropertyInfo pix2 = (PropertyInfo)getPropMethod.Invoke(type, new object[] { "Pixels" }); // second call - MethodAccessException
    }
    catch (Exception ex)
    {
    }
}

方法 GetProperty 的第一次调用执行成功并且没有抛出异常。但是第二次调用 - methodInfo.Invoke 抛出 MethodAccessException - 为什么会发生这种情况？

异常和堆栈跟踪:

MethodAccessException: Attempt by security transparent method 'System.Type.GetProperty(System.String)' to access security critical method 'SilverlightApplication3.MainPage.temp()' failed.

in System.RuntimeMethodHandle.PerformSecurityCheck(Object obj, RuntimeMethodHandleInternal method, RuntimeType parent, UInt32 invocationFlags)
in System.RuntimeMethodHandle.PerformSecurityCheck(Object obj, IRuntimeMethodInfo method, RuntimeType parent, UInt32 invocationFlags)
in System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
in System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
in System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
in SilverlightApplication3.MainPage.temp()

Answer 1

Silverlight 中的反射仅限于编译时可用的内容，也许您第一次调用函数时条件已满足，但在第一次调用后某些内容发生变化并且反射无法执行。

In Silverlight, you cannot use reflection to access private types and members. If the access level of a type or member would prevent you from accessing it in statically compiled code, you cannot access it dynamically by using reflection.

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