本文通过举例介绍如何实现向 Active Server Pages (ASP) 返回记录集的 Visual C++ 组件对象模型 (COM) 对象。
错误实现该对象可能会导致内存泄漏或下列错误之一：
The operation requested by the application is not allowed if the object is closed.
- 或 -
类型不匹配
- 或 -
error 'ASP 0115' - A trappable error occured in an external object
使用下列步骤实现一种方法，该方法从 Visual C++ COM 对象向 Active Server Pages 返回记录集。
| 1. |
创建一个名为“PassRs”的 ATL DLL 项目。 |
| 2. |
插入一个名为“PassRsObj”的 ATL 对象。 |
| 3. |
添加包含以下信息的方法：Method Name: TestMethod
Parameters : [out, retval] LPDISPATCH* ppRecordset
|
| 4. |
在对象的实现文件中包括下面一行：#import "msado15.dll" no_namespace rename("EOF", "adoEOF")
|
| 5. |
按如下所示实现该方法：
注意：您必须先将 UID=<username> 和 pwd=<strong password> 更改为正确的值，然后才能运行此代码。请确保该 UID 具有在数据库中执行此操作所需的适当权限。
STDMETHODIMP CPassRsObj::TestMethod(LPDISPATCH *ppRecordset )
{
_ConnectionPtr pConn;
_RecordsetPtr pRs;
pConn.CreateInstance(__uuidof(Connection));
pRs.CreateInstance(__uuidof(Recordset));
pConn->Open("DSN=pubs;uid=<username>;pwd=<strong password>;", (BSTR) NULL, (BSTR) NULL, -1);
//Client side cursor is required for disconnected recordsets
pRs->CursorLocation = adUseClient;
pRs->Open( "select * from authors",
pConn.GetInterfacePtr(),
adOpenKeyset, adLockOptimistic, -1);
// Disconnect the recordset
pRs->PutRefActiveConnection(NULL);
//Clone the recordset.
//NOTE: Recordset to be cloned must support bookmarks
pRs->Clone(adLockOptimistic)->QueryInterface(IID_IDispatch, (void**) ppRecordset);
pRs->Close();
pConn->Close();
pRs = NULL;
pConn = NULL;
return S_OK;
}
|
| 6. |
创建含有以下代码的 ASP 页：<%
Dim rsTest, oTestPassRs
Set oTestPassRs = Server.CreateObject("PassRs.PassRsObj")
Set rsTest = oTestPassRs.TestMethod()
Do
Response.Write ( "Value in Record = " & rsTest(1) & "<BR>" )
rsTest.MoveNext
Loop until rsTest.EOF
rsTest.Close
Set rsTest = Nothing
Set oTestPassRs = Nothing
%>
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