COM注册什么时候需要注册APPID .

COM 7.0以后有这样一个宏DECLARE_REGISTRY_APPID_RESOURCEID

 

在VS03以后的版本中，ATL工程中会自动添加这样的代码

class CXXModule : public CAtlDllModuleT< CXXModule >
{
public :
 DECLARE_LIBID(LIBID_xinstallerLib)
 DECLARE_REGISTRY_APPID_RESOURCEID(IDR_XX, "{classid}")
};

CXXModule _AtlModule;

_CAtlDllModuleT继承自CAtlModule

 

看MSDN解释说AppId在DCOM中使用，主要是为了集中注册表中分散的属性值，觉得这个解释相当含糊。

 

那么什么时候才需要指定这个AppId呢？看到一个老外回答这个问题，不翻译了，原文看着比较好。

You need to specify an appid if one of the following is true:

1. Your COM object is hosted in a service
2. Your COM object has custom launch permissions
3. Your COM object has custom access permissions
4. You want to specify a default bitness for the COM server when launching an out-of-proc COM object. 
5. Your COM object runs as another user
6. Your COM object needs to run on another system (unless you specify a COSERVERINFO in your call to CoCreateInstanceEx)
7. Your COM object needs to set the default authentication level (used if you don't call CoInitializeSecurity directly)
8. Your COM object needs to specify the RPC endpoints for communication (or the TCP port number, etc)
9. Your COM object should run on the same machine as the storage (ActivateAtStorage)
10. Your COM object runs using the DLL surrogate
11. Your COM object needs to set its software restriction trust level

If those are true, you need an appid, otherwise it's unnecessary (and takes up space on the disk).