接口继承和铸造 [英] Interface Inheritance and Casting

问题描述

我创建了我从另一个（COM）接口继承的接口：

I have created an interface which I am inheriting from another (COM) interface:

public interface IDTSComponentMetaData : IDTSComponentMetaData90 { }

这就是它。

这背后的原因是，这取决于哪一个版本的SQL Server我正在与工作的，所述碱可以是IDTSComponentMetaData90（2005）或IDTSComponentMetaData100（2008）。而不是条件编译代码每个参考IDTSComponentMetaData90 / IDTSComponentMetaData100，我想使用的版本无关的接口，这将只是换合适的实际接口。

The reason behind this is, depending on which version of SQL Server I am working with, the base may be IDTSComponentMetaData90 (2005) or IDTSComponentMetaData100 (2008). Rather than conditionally compile every reference to IDTSComponentMetaData90 / IDTSComponentMetaData100 in code, I'd like to use the version-neutral interface which will simply wrap the proper real interface.

问题是SSIS通过我在一个关键的点对象到原生界面，我需要将其转换为我的封装接口：

The problem is that SSIS passes me an object to the native interface at one key point, and I need to cast it to my wrapper interface:

#if SQL2005
public void Initialize(IDTSComponentMetaData90 c,IServiceProvider s) {
#elif SQL2008
public void Initialize(IDTSComopnentMetaData100 c,IServiceProvider s) {
#endif
  m_ComponentMetaData = (IDTSComponentMetaData) c;
  m_ServiceProvider = s;
}

这编译没有问题，但在运行时，我得到一个'无法投类型的COM对象的系统.__ ComObject'的接口类型MyNameSpace.IDTSComponentMetaData。此操作失败的原因是对IID失败，因为下面的错误接口{483E01E7-001C-35E4-Ac9f-4B0C1B81E409}'的COM组件调用QueryInterface：不支持此接口（异常来自HRESULT：0x80004002（E_NOINTERFACE））

This compiles with no problem, but at run time, I get an 'Unable to cast COM object of type 'System.__ComObject' to interface type 'MyNameSpace.IDTSComponentMetaData'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{483E01E7-001C-35E4-Ac9f-4B0C1B81E409}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

是我在做什么完全错了？

Is what I am doing totally wrong?

推荐答案

任何原因你根据SQL Server版本不只是别名接口？

Any reason you don't simply alias the interface depending on SQL Server version?

#if SQL2005
using IDTSComponentMetaData = IDTSComponentMetaData90;
#elif SQL2008
using IDTSComponentMetaData = IDTSComopnentMetaData100;
#endif

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