请问一个关于ado连接数据库的问题

我的的代码是这样写的
HRESULT hr;
hr = this->m_Connection.CreateInstance("ADODB.Connection");

if(SUCCEEDED(hr))
{
hr=this->m_Connection->Open((_bstr_t)this->m_Connstr,"","",adModeUnknown);
}
ado连数据库为什么在open这个地方出现了异常 数据库连接的代码是正确的  为什么会在这里抛出异常啊
hr=this->m_Connection->Open((_bstr_t)this->m_Connstr,"","",adModeUnknown);