方法只能在Type堪称为这Type.IsGenericParameter是真实的 [英] Method may only be called on a Type for which Type.IsGenericParameter is true

问题描述

我得到的，它使用反射抛售一些对象属性，像下面的代码例行此错误。

I am getting this error on a routine which uses reflection to dump some object properties, something like the code below.

MemberInfo[] members = obj.GetType().GetMembers(BindingFlags.Public | BindingFlags.Instance) ;

foreach (MemberInfo m in members)
{
    PropertyInfo p = m as PropertyInfo;
    if (p != null)
    {
       object po = p.GetValue(obj, null);

       ...
    }
}

实际的错误是异常被抛出由调用的目标
与内部异常方法只能叫上键入这Type.IsGenericParameter是真实的。

The actual error is "Exception has been thrown by the target of an invocation" with an inner exception of "Method may only be called on a Type for which Type.IsGenericParameter is true."

在这个阶段在调试器的obj显示为

At this stage in the debugger obj appears as

  {Name = "SqlConnection" FullName = "System.Data.SqlClient.SqlConnection"}

与该类型System.RuntimeType

with the type System.RuntimeType

该方法m是{System.Reflection.MethodBase DeclaringMethod}

The method m is {System.Reflection.MethodBase DeclaringMethod}

注意obj是类型System.RuntimeType和成员包含188项而一个简单的
typeof运算（System.Data.SqlClient.SqlConnection）.GetMembers。（System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance）只返回65

Note that obj is of type System.RuntimeType and members contains 188 items whereas a simple typeof(System.Data.SqlClient.SqlConnection).GetMembers(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance) only returns 65.

我试过两个OBJ和p.PropertyType检查isGenericParameter，但是这似乎是大多数属性虚假包括那些p.GetValue的作品。

I tried checking isGenericParameter on both obj and p.PropertyType, but this seems to be false for most properties including those where p.GetValue works.

所以，到底什么是键入该Type.IsGenericParameter是真的，更重要的
我怎么避免这个错误没有一个try / catch？

So what exactly is a "Type for which Type.IsGenericParameter is true" and more importantly how do I avoid this error without a try/catch?

推荐答案

首先，你在不正确的假设做了，那就是，你认为成员返回一个实例成员<$的C $ C> System.Data.SqlClient.SqlConnection ，它没有。什么已恢复为的System.Type 的一个实例的成员。

Firstly, you've made in incorrect assumption, that is, you've assumed that members has returned the members of an instance of System.Data.SqlClient.SqlConnection, which it has not. What has been returned are the members of an instance of System.Type.

从MSDN文档<一个HREF =http://msdn.microsoft.com/en-us/library/system.type.declaringmethod.aspx> DeclaringType ：

获取 DeclaringMethod 属性
上的类型，其 IsGenericParameter
属性是假抛出一个
出现InvalidOperationException 。

所以...这是可以理解的，一个出现InvalidOperationException 被抛出，因为自然的，你不处理一个开放式泛型类型在这里。见的马克Gravells回答开放泛型类型的说明。

So... it's understandable that an InvalidOperationException is being thrown, since naturally, you're not dealing with an open generic type here. See Marc Gravells answer for an explanation of open generic types.

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