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++(www.cppentry.com)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());
}
::CoUninitialize();
} |
使用GetItem(x)和Item[x]
下面是VB中关于Item()的标准与交互语法的演示。
Public Sub GetItemItem
Dim rs As New ADODB.Recordset
Dim name as String
rs = rs.Open "authors", "DSN=pubs;", adOpenDynamic, _
adLockBatchOptimistic, adTable
name = rs(0)
' -or-
name = rs.Fields.Item(0)
rs(0) = "Test"
rs.UpdateBatch
' Restore name
rs(0) = name
rs.UpdateBatch
rs.Close
End Sub |
以下则是VC++(www.cppentry.com)关于Item的演示
当访问collection中的Item时，索引值2必须被转换为long类型以确保正确的构造函数被调用。
#import "c:\Program Files\Common Files\System\ADO\msado15.dll" \
no_namespace rename("EOF", "EndOfFile")
#include <stdio.h>
void main(void)
{
CoInitialize(NULL);
try {
_RecordsetPtr rs("ADODB.Recordset");
_variant_t vtFirstName;
rs->Open("authors",
"Provider=sqloledb;Data Source=a-tima10;"
"Initial Catalog=pubs;User Id=sa;Password=;",
adOpenStatic, adLockOptimistic, adCmdTable);
rs->MoveFirst();
// Note 1.取得一个字段的名称
vtFirstName = rs->Fields->GetItem((long)2)->GetValue();
// -or-
vtFirstName = rs->Fields->Item[(long)2]->Value;
printf( "First name = '%s'\n", (char*) ((_bstr_t) vtFirstName));
rs->Fields->GetItem((long)2)->Value = L"TEST";
rs->Update(vtMissing, vtMissing);
// 恢复原名称
rs->Fields->GetItem((long)2)->PutValue(vtFirstName);
// -or-
rs->Fields->GetItem((long)2)->Value = vtFirstName;
rs->Update(vtMissing, vtMissing);
rs->Close();
}
catch (_com_error &e)
{
printf("Description = '%s'\n", (char*) e.Description());
}
::CoUninitialize();
}
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