_ConnectionPtr  pCn("ADODB.Connection");

   _variant_t      vtTableName("authors"),

                   vtCriteria;

   long            ix[1];

   SAFEARRAY       *pSa = NULL;

   pCn->Open("DSN=pubs;User ID=sa;pwd=;Provider=MSDASQL;", "", "",

               adConnectUnspecified);

// Note 2, Note 3

   pSa = SafeArrayCreateVector(VT_VARIANT, 1, 4);

   if (!pSa) _com_issue_error(E_OUTOFMEMORY);

// 为第三个元素赋值TABLE_NAME(索引值2).

   ix[0] = 2;     

   TESTHR(SafeArrayPutElement(pSa, ix, &vtTableName));

// 由于Variant没有SafeArray的构造函数，所以手工设置Variant的数据类型和值。

   vtCriteria.vt = VT_ARRAY | VT_VARIANT;

   vtCriteria.parray = pSa;

   pRs = pCn->OpenSchema(adSchemaColumns, vtCriteria, vtMissing);

   long limit = pRs->GetFields()->Count;

   for (long x = 0; x < limit; x++)

      printf("%d: %s\n", x+1,

         ((char*) pRs->GetFields()->Item[x]->Name));

// Note 4

   pRs->Close();

   pCn->Close();

   }

   catch (_com_error &e)

   {

   printf("Error:\n");

   printf("Code = %08lx\n", e.Error());

   printf("Code meaning = %s\n", (char*) e.ErrorMessage());

   printf("Source = %s\n", (char*) e.Source());

   printf("Description = %s\n", (char*) e.Description());

   }

   CoUninitialize();

}

使用属性的Get/Put/PutRef

在VB中，属性的名称并未被检验，无论它是被读取、被赋值，或者赋予一个引用。

Public Sub GetPutPutRef

Dim rs As New ADODB.Recordset

Dim cn As New ADODB.Connection

Dim sz as Integer

cn.Open "Provider=sqloledb;Data Source=yourserver;" & _

         "Initial Catalog=pubs;User Id=sa;Password=;"

rs.PageSize = 10

sz = rs.PageSize

rs.ActiveConnection = cn

rs.Open "authors",,adOpenStatic

'''' ...

rs.Close

cn.Close

End Sub

以下是VC++关于Get/Put/PutRefProperty的演示

1．这个例子演示了省略字符串参数的两种形式：一种是采用常量strMissing，另一种则是由编译器自动生成一个临时的存在于Open方法使用期间的_bstr_t。

2．因为操作数已经是(IDispatch *)的指针，所以没有必要将rs->PutRefActiveConnection(cn)的操作数再进行类型转换。

#import "c:\Program Files\Common Files\System\ADO\msado15.dll" \

   no_namespace rename("EOF", "EndOfFile")

#include <stdio.h>

void main(void)

{

   CoInitialize(NULL);

   try

   {

      _ConnectionPtr  cn("ADODB.Connection");

      _RecordsetPtr   rs("ADODB.Recordset");

      _bstr_t         strMissing(L"");

      long            oldPgSz = 0,

                      newPgSz = 5;

// Note 1

      cn->Open("Provider=sqloledb;Data Source=a-tima10;"

         "Initial Catalog=pubs;User Id=sa;Password=;",

         strMissing, "",

         adConnectUnspecified);

      oldPgSz = rs->GetPageSize();

   // -or-

      oldPgSz = rs->PageSize;

      rs->PutPageSize(newPgSz);

   // -or-

      rs->PageSize = newPgSz;

// Note 2

      rs->PutRefActiveConnection( cn );

      rs->Open("authors", vtMissing, adOpenStatic, adLockReadOnly,

               adCmdTable);

      printf("Original pagesize = %d, new pagesize = %d\n", oldPgSz,

               rs->GetPageSize());

      rs->Close();

      cn->Close();

   }

   catch (_com_error &e)

   {

      printf("Description = %s\n", (char*) e.Description());

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